What and spoil all the fun of discovery? There are so few books out there on clowning that all of them have something interesting to say. What I did was use my local libraries and found some books there, and some I aqcuired through the national inter-library loan system. Talk to you local reference librarian about it. For book titles, check out the
Amazing Clown Rescources thread towards the bottom is a list of books. I need to add more to it because some one posted some more to the thread and I haven't updated the first post for it yet.
But yeah... explore and search. There is not enough stuff out there to be too picky. Looking at the not so great stuff is almost as valuble as looking at the really good stuff.