Many of the most useful books are now out of print, but there are some listed here that should be readily available and will be of use to many collectors.
Old Time Telephones! Technology Restoration and Repair
by Ralph O Meyer. Deals with United States telephones, history, circuits etc. Recently revised, it it essential not only for U.S. collectors but for those in any country where the U.S. phones were used. Currently $29.95 U.S, and available from Amazon, Phoneco, or Schiffer Publishing. Although it has now been considerably updated and expanded, even the old version is worth obtaining.
History of the Telephone in New South Wales
by Jim Bateman. This is essential for Australian and New Zealand collectors. It was originally released in 1980 and some of the information is becoming a bit dated in light of more recent research, but it manages to cover just about every phone used in Australia up to the Telecom era. Most phones are illustrated so it is an invaluable identification guide as well as a history reference. Recently reprinted and available from the Australasian Telephone Collectors Society, P.O. Box 396, Moorebank NSW 1875, Australia for $25 Australian in A4 size or $22 in pocket size. Price includes postage within Australia.
by Andrew Emmerson. This little book is probably out of print now, but it is readily available from eBay for around $8 to $10 U.S. It is a brief but detailed history of the telephone in Britain. It includes many well-photographed illustrations and useful information like manufacturers' codes. Well worth tracking down.
The Telephone Book
by O. Boettinger. A history of the Bell / AT&T companies up to 1976. A little biassed perhaps but comprehensive, beautifully illustrated, and a good read by itself. It is also out of print but readily available on eBay and through secondhand bookshops for around $10 to $30.
Telephones - Their Construction and Fitting by F G Allsop. Out of print, but turns up sometimes on eBay. This little British book includes useful information on early telephones, circuitry and construction techniques. Well illustrated. Late 1890s to about 1920s.
Telephony by Samuel G McMeen and Kempster Miller. Subtitled "A comprehensive and detailed exposition of the Theory and Practice of the Telephone Art", and that just about sums it up. Detailed coverage of early U.S. telephony as it existed around 1900 - 1920. Well illustrated, and covers early Automatic Electric switchgear. Fairly easy to get through eBay or secondhand bookstores.
The Practical Telephone Handbook by J Poole. Poole was a British Post Office engineer around the turn of the century, and this book covers BPO practice and telephone history from the early days from the European viewpoint. Not too easy to find, but worth tracking down.
Telephony by T E Herbert and W S Proctor. Both BPO engineers, and covers the period from around 1910 to the 1930s, depending on which edition you get. Strong on theory and circuits rather than telephones, but has many useful bits.