A list of every guide book I know of that includes overnight walks. Some are out of print and only available in libraries or as second hand books.
As the state with the largest population in Australia, you would expect good information. The major areas are well covered although there are extensive walking regions with little published information (particularly in the north).
120 Walks in New South Wales (5th edition), by Tyrone Thomas, published by Hill of Content, 1999. Mainly one day walks with descriptions of 10 overnight walks. Probably out of print, price was around A$25.
Classic Blue Mountains Walks (1st edition) by David Noble, published by WILD magazine, 1996. A small guide of 28 pages of brief track notes for 10 mountains scattered around Australia. Price is around A$7.50.
Classic New South Wales Walks (1st edition) by John Chapman, published by WILD magazine, 1997. A small guide of 24 pages of brief track notes for 7 overnight walks. Price is around A$7.50.
The Colo Wilderness (1st edition) by Anthony Dunk, published by Envirobook, 1999 ISBN 0 85881162 6. A small 78 page guide describing walks in the large wilderness area to the north of the Blue Mountains. The book contains a mixture of one day and multiple day walks for experienced bushwalkers. Price is around A$13.
Yengo & Dharug National Parks (1st edition) by Anthony
Dunk, published by Envirobook, 2001 ISBN 0 85881183 9. A
small 92
page guide describing walks in this relarively unknown park north of
Sydney. The book is essentially one day walks but does contain three
extended walk suggestions for experienced bushwalkers. Price
is around A$14.
Bushwalks In The Sydney Region, Volume 1 (4th edition) ISBN 0 95875903 0, & Volume 2 (3rd edition) ISBN 0 95875908 1, editors Lord & Daniel, published by National Parks Association. Includes many one day walks with some overnight and longer trips. Volume 1 covers 86 walks of which 20 are overnight and longer and volume 2 covers 80 walks of which 18 are overnight or longer. Price is $17 for volume 1 and $18 for volume 2.
The Ensign Barrallier Walk : Katoomba to Mittagong Track by Robert Sloss, self published, 1995. A 42 page booklet describing a 9 day walk from Katoomba through Yarranderie to Mittagong. While the walk is relatively interesting, there is actually no such track known by this name. Out of print, price was around $7.90
Hiking In The Blue Mountains by Robert Sloss, self published 1997, ISBN 0 9586512 1 3. A 34 page booklet describing walks in the Katoomba region of the Blue Mountains. Most are one day walks but there are some useful notes for overnight walks particularly to Mt Solitary and Kanangra Walls. Out of print, price was around $7.90.
Mittagong - Nattai Bushwalking by Robert Sloss, self published 1998, ISBN 0 9586512 8 0. A 27 page booklet to the southern section of the Blue Mountains. Includes 3 overnight walks. Very useful as no other books cover this area. Out of print, price was around $7.90.
Bushwalking in Kosciusko National Park (2nd edition), by Charles Warner, published by Charles Warner, 1989, ISBN 0 9592036 2 1. Covers all regions of the park and has no detailed track notes but instead provides descriptions of all the worthwhile features. Suitable for experienced walkers to plan trips. Price is around A$20.
Snowy Mountains Walks (8th edition), published by Geehi Walking Club, 2001, ISBN 0 9599651 4 9. Describes the major routes which can be one day walks or linked into multi-day walks. Be careful as the note detail and gradings for range top walks is very different compared to the hard routes through the gorges. A well known book with the first edition in 1961. Price is around A$25.
A Guide to North-eastern New South Wales (4th edition),
published
by University of New England Mountaineering Club, 1984 (is there
a newer edition?). A very comprehensive guide, provides very brief
notes to a huge number of routes and tracks from Tamworth to the
coast and north to the Queensland border. Out of print, price unknown.
A Walkers Guide to The Tops to Myall's Heritage Trail (1st edition), published by Lions Club of Tea Gardens, 1993, ISBN 0 9590026 3 4. A thin book to the signposted 220km, eleven day walk from Barrington Tops to the coast. It's a one way track as there are only markers in one direction. Out of print, price was around A$6.
Treks In New South Wales (1st edition) by Neil Paton, published by Kangaroo Press, 1986, ISBN 0 86417 079 3. Describes 10 overnight or longer walks in the parks around Sydney. Out of print.
The Great North Walk (1st edition) by Garry McDougall and Leigh Shearer-Heriot, published by Kangaroo Press, 1988, ISBN 0 8647 134 X. The guide to the 250 km Great North Walk track linking Sydney to Newcastle. Out of print. A second edition was published by Simon and Shuster in 1996 with the identical ISBN - I have been unable ot obtain a copy to determine if the information was updated or it was simply a reprint of the first edition which the use of the same ISBN indicates (comments from others about the 2nd edition are welcomed).
The Hume and Hovell Walking Track Guidebook (1st edition), by Harry Hill, published by Crawford House Press, 1993, ISBN 1 86333 066 6. The guide to the 310 kilometre long distance Hume and Hovell Track that runs from Wee Jasper to the Hume Highway north of Albury. Essential if you intend to walk this historical track. Out of print, price was around A$20.
Fitzroy Falls and Beyond (1st edition), published by The Budawang Committee, 1988, ISBN 0 9593381 2 8. A comprehensive book about Morton National Park. While only 76 of the 350 pages are about bushwalking it is worth obtaining if you wish to explore this park. Current price and availability unknown.
Pigeon House and Beyond (1st edition), published by The Budawang Committee, 1982, ISBN 0 9593881 0 1. The Budawangs are the southern part of the Morton National Park. Like its companion book above only 38 of the 300 pages are about bushwalking but they are helpful for planning trips. Current price and availability unknown.
Bushwalking In The Budawangs (3rd edition) by Ron Doughton, published by Envirobook, 2004, ISBN 0 85881 072 7. Describes most of the tracks and routes in the range. Well worth obtaining if walking here. Price about A$25.
70 Walks in Southern New South Wales and ACT (2nd edition), by Tyrone Thomas, published by Hill of Content, 199?, ISBN 0 85572 289 4. Mainly one day walks with 11 overnight bushwalks hidden in its pages. Probably out of print, price was around A$22.
Federation Track - from Circular Quay to Stanwell Park, by
Bill Avery, published by Kangaroo Press, 1996, ISBN 0 86417 813
1. The track notes are really just for one day walks from Sydney
south past Royal National Park. Included here as the book describes
a proposal to link the major long distance walks together into
something the author has called The Federation Track. Out of print,
price was around $13.
Take A Walk in Blue Mountains National Park (2nd edition), by John & Lyn Daly, published by Take A Walk Publications, 2000, ISBN 978 0 9577931 6 3. Attempts to describe all official tracks and describes them all briefly. Basically is for one day walks with just 2 suggestions for overnight walks. Price is around $25.
Take A Walk in a National Park Sydney to Port Macquarie (1st edition), by John & Lyn Daly, published by Take A Walk Publications, 2000, ISBN 0 95779311 1. Attempts to describe all official tracks and does describe them all briefly. Very useful as many of these parks have no other published track notes. Basically is for one day walks with just 3 suggestions for overnight walks. Price is around $22.
Take A Walk in a National Park Port Macquarie to Brisbane (1st edition), by John & Lyn Daly, published by Take A Walk Publications, 2000, ISBN 0 95779312 X. Attempts to describe all official tracks and does describe them all briefly. Very useful as many of these parks have no other published track notes. Basically is for one day walks with just 4 suggestions for overnight walks. Currently out of print, was around $22.
Take A Walk in New South Wales National Parks South-Eastern Zone (1st edition), by John & Lyn Daly, published by Take A Walk Publications, 2002, ISBN 0 95779313 8. Attempts to describe all official tracks and does describe them all briefly. Basically is for one day walks with 10 suggestions for overnight walks. Currently out of print, was around $25.
Take A Walk in Kosciuszko National Park (1st edition) by John & Lyn Daly, published by Take A Walk Publications, 2010, ISBN 978 0 9577931 8 7. Mainly day walks with 7 overnight walks plus the Australian Alps Walking Track (AAWT) described in 3 sections. Fairly comprehensive although descriptions are at times briefer than in other guides. Price is around A$35
Exploring the Jagungal Wilderness by Robert Green, published
by
Robert Green 2015. A comprehensive guide for off-track walking east of
the Grey Mare Fire Trail in the Jagungal Wilderness section of the
Kosciuszko National Park. Essential reading for anyone wishing to
explore this interesting area. Price is around $30
For books to the Australian Alps Walking Track, refer the Victoria guide book page.