Where to find books
For most of us, the specialty used bookstore has evolved into chains, some of whom have a reasonable selection of military books, but for the most part, browsing the shops for good books on the Great War and the CEF in particular is becoming harder.
Fortunately there are a number of good on-line sources for new and used books.
There is a strong likelihood that many of the books in this database are available at your local library or available through inter-library loan. The Canadian inter-library program is quite good and while it may take a while to get the material, the price can't be beat!
Chapters (in Canada) always seems to have a decent selection of new books.
Barnes & Nobel (in the US) has a reasonable selection on their web site.
Major Military Book Sites
CEF Books. Norm Christie's site. Great selection, great service. CEF Books has reprinted a number of classics, and the only way that he will continue to do this is if we buy his books. One additional touch is that Norm has signed every book of his (the King & Empire series) I've bought from him.
Service Publications. Another good source for Canadian Military books.
The Archive Books CD Project has fully searchable books available on CD, including a number related to the CEF.
Marway Militaria provides a good source of Books, in addition to other Canadian military and police collectibles.
New and Used composite searches
abeBooks.com is the largest network of used book shops and has a tremendous selection of out-of-print books. There has only been 1 title that I've searched for that hasn't shown up there (and it was pretty obscure). Note that they rely on the individual shops to keep the inventory updated and I've been disappointed on a couple of occasions because the book I ordered wasn't available when it came time to process the order.
BookFinder.com. Another excellent source for used and out of print books. Has a great search engine that makes finding first editions or signed copies easier.
Books from the UK
Naval and Military Press large selection of books. It's worth getting on their mailing list just to get their quarterly catalog. Reading this can take a few hours! If you don't specify airmail for shipments, expect to wait quite a few months for the shipment to arrive
Tom Morgan Books. Good selection and reasonable prices.
If you are willing to wait, there are some great bargains that come up on eBay. Before purchasing anything on eBay, I would strongly advise that you check the title on abeBooks. That will allow you to identify the market value of the book and allow you to set your spending limit appropriately.
If there are book sources that are missing and you feel should be added to this list, please let me know.