I think you have to be more specific as to which type of knives the collector is trying to understand and build a collection. But since you are here and I can only knowledgeably speak on customs knives thats the direction I will go.
IMO, it takes much more than just books and a data base to understand collecting custom knives. Though examining the "Knives Annuals" and reading all the knife publications is a good start. Going to knife shows, especially Blade is very helpful in getting to see and handle just about every custom out there and offers an opportunity to meet and talk to many makers. There's usually good seminars on collecting taught by knowledgeable dealers and/or collectors at the major knife shows.
Reading and participating on the right forums such as this one is extremely important.
IMO, the most valuable tool for a new collector in understanding and starting a collection is to follow the dealer websites on a daily basics. They contain an abundance of custom knife information form photos and descriptions on all types and styles of knives, to bios on the makers. Most importantly, they allow you to determine and track what knives and makers are selling both consistently and which one are currently hot. And as important, shows you at what prices they are selling for.
A collector can scan the top dozen dealer sites for the information above in about thirty minutes a day.
If I had to give advise in a few words, it would be to be very patience and try to determine where your passion lie before buying.
Just quickly scratched the surface, but hope it helps.