I have a pretty large library of the books I've read going back to many that were in my Fathers library. I don't really collect rare books but some have just turned out that way. The real gem of what I have are my Fathers many hunting and shooting books. He and my Mother were great duck and upland game hunters and these books of his date from before the war right up until he passed in the 1980's. When I'm looking for a rare book I've found these sites useful :
www.bookfinder.com, www.biblio.com and
www.used.addall.com . All these sites and others were once available on a website called "Literascripta" but it disappeared as this most recent generation has switched to other forms of amusement.