Have posted a few book reviews, thought it would be appropriate to list some sources for them.
Skip over this part and go straight to the links if you want, but knowing how books are published may help in finding them for purchase. There are basically three ultimate sources of books.
First, there are the established publishing houses. They tend to deal in books that will make it into brick and mortar book stores. Writers want to publish with these companies as they get the most exposure that way, and there is a lot of prestige in having a book picked up by a publisher. These books are sold to stores at usually an almost 50% discount off the cover price. If the store does not sell it then they usually have the right to return the books for a refund, and shipping is paid for by the publisher (or the publisher may direct them to destroy the books, which sometimes does not happen). Those surplus books end up on clearance racks, or in the used or surplus market. About half of the paperback books printed are ultimately destroyed, believe it or not. Phillip's books (e.g., The Complete Guide to Locks and Locksmithing) was published through one of these publishing houses, which is why it shows up in brick and mortar stores at times. Part of its popularity stems from its availability. These books will have some professional designing and editing and will appeal to the mass-market. Go to any bookstore and they can look up these books and order them, and Amazon can order them as well. For a publishing house to accept a new lock related book would generally indicate a book that is either worth a very high price or is a book with wide appeal. Pulford's book on high security locks found its way to a publisher, as did Deviant Ollam's books on picking and locks. Other than that I am not familiar with many locksmithing related books being picked up by a publisher in many years. Even with them, the publisher was a small one that dealt in technical books. The ISBN number is the universal number for books published and any book from a big publishing house will have one.
Second, there are the small, niche, trade publishing companies. They may not bother with an ISBN number / bar code on the book. Either no brick and mortar store would stock them, or the information is sensitive enough that the publishers want to have some control over the distribution. That would include publications by the National Locksmith, ALOA, etc. These can be great books, but challenging to find. Sometimes they have typos, but tend to be technically correct as none of these companies want to put their name on a book that will dishonor them. Drawback here is the risk of obsolete material. If one of these publishers had a run of 2,000 copies made and twenty years later they still have 1,000 left, they might not have them destroyed and pay an author to revise the book--they could be tempted to keep on selling the partly obsolete books. Buyer beware, some of these books are on the obsolete side. Bookstores and Amazon will not be able to order these books. It is either find out who sells them or find them used.
Third, there are self-published books. Anyone who spends some time at it can publish whatever they want. There are some self-published locksmithing books out there, and probably there will be more every year. They can be e-books and/or paper books. Paper books are printed on-demand and if one orders through Amazon in California a book pops out of a printing machine at Ingram in Nashville, TN (among other places) the next day and is drop shipped to the customer with an Amazon label on the box. These books will tend to show up on Amazon, and Amazon has Create Space to streamline self-publishing. Most brick and mortar stores will not touch self-published books with a ten-foot pole. But then, brick and mortar stores are disappearing every day. More of publishing is moving in this direction. There used to be a lot of stigma with self-publishing (i.e., the vanity presses where one paid a lot of money to print a few books, just to be able to say they were an author), but technology is pushing things in this direction and some "publishable" authors are electing to self-publish so as to have higher profits, more control of the process, and greater speed (publishing houses usually release books in the spring and fall, and it may take one or two years for them to print a book they have under contract). It means a lot more books will be out there, but it will be buyer-beware more than ever in sorting out the good from the bad. Even before modern print-on-demand printing and e-books, some locksmiths self-published books, the Shankle and Shankle: Comprehensive Manual of Locksmithing being an example. These books will usually have ISBN numbers if the seller wants to sell through Amazon.
Enough of that, here are some sources:
https://shop-foley-belsaw.com/foley/29.cat -- Will sell without any hassles, but not always the best price. They even sell the Kwikset re-keying guide, that anyone can download for free. They do run discounts from time to time if one signs up for the catalog.
http://www.thenationallocksmith.com/pdf/TNLCatalog2015.pdf -- Their e-commerce site is blocked to keep out us riff-raff, but a phone call or printed order form mailed in may get through? The irony is that Foley-Belsaw sells The National Locksmith lock-picking and safe-cracking books to anyone, but books on SFIC, aluminum store-front doors, etc., are kept locked up at this site.
http://www.aloastore.com/Subcategories.aspx?ID=1&Cat=Education -- They keep out the riff-raff also, one has to have a login to actually order.
http://www.sievekingprodco.com/locksmithguidebooks.html -- Have not tried ordering from here, but it was found in a search.
http://www.locksmithingeducation.com/ -- Have not tried ordering from here, it was found in a search.
http://locksoft.com/books/ -- Have not tried ordering from here, it was found in a search as well.
Some lock pick or locksmith commerce sites also sell books.
Besides Amazon and eBay, sources for used or overstock books are below. Note that if a book lacks an ISBN number they will not likely show up in these sources. Best bet for books without ISBN's are eBay and Amazon. Amazon has recently made it more difficult to list used books for the first time that lack ISBN numbers, so eBay may be the best bet in the future as new ISBN-less books come on the market.
http://www.alibris.com/ -- A used-book alternative to Amazon.
https://www.abebooks.com/ -- A used-book alternative to Amazon.
http://www.thriftbooks.com/ -- A used-book alternative to Amazon.
(note: a lot of used books for sale are cross-posted to multiple sites, so a book for the same price on three sites does not mean it is the "going price", it may be the very same book).
https://www.hamiltonbook.com/books --Mainly surplus mass-market books, Phillip's book sometimes shows up here at a good discount.
Note that some public libraries will lend books via interlibrary loan--that can be a no-cost way to read some locksmithing books, although that would tend to only cover books from established publishing houses.
If anyone has other leads on locksmithing book suppliers please post them.