This terrific hardcover volume, written and compiled by John Landis, has sadly fallen out of print.
... luckily, it's being reissued in paperback later this summer!
I checked this out of the library last year, and it's a tremendous amount of fun: basically a compendium of monsters represented by stills, publicity shots, and posters with short descriptions by Landis. They're sorted be theme, and interspersed between these are interviews with folks like Harryhausen, Christopher Lee, Guillermo del Toro, Joe Dante, etc. - all the interviews revolving around just what is a monster?
It's well designed, and just pure candy for folks like us.