Start with Of Mice and Magic by Leonard Maltin and Jerry Beck. That book only covers the "Golden Age of Hollywood Animation" (late 1920s-early 1960s) and about half the book is about Walt Disney, but it's a good place to start. It's reader friendly and covers all the basics about those studios and how animation went from Steamboat Willie to big business by the 1970s, when the book was written.

More recently, there's A World History of Animation which I haven't read but goes beyond just Hollywood animation. It's received good reviews on Amazon, so it might be worth checking out.

I have also read Cartoons by Giannalberto Bendazzi, Hollywood Cartoons by Michael Barrier, and Before Mickey by Donald Crafton, and I wouldn't recommend any of them. Bendazzi's book is way too disorganized to be useful, and reads more like an encyclopedia anyway, spending a few paragraphs or maybe a page or two on each topic. Barrier's book assumes the reader already knows all the basics of Hollywood animation, so it's more like "an insider's guide of what really want on behind the scenes of the Golden Age of Animation" than an actual history book. And Before Mickey only covers the silent era and the prose of the book is really, really dry. It's written like a research paper, but without enough details to justify the writing style.

There are a couple other more recent books that cover animation as a whole, and you might have good luck with those, but they seem to be mostly textbooks. Beyond that, most books on animation deal with a specific topic, like anime, or a specific anime series, or Disney, or Warner Brothers, or one of the other studios or filmmakers.

Start with Of Mice and Magic and maybe A World History of Animation. From there, pick whatever animation topic interests you, and you may find some good books on that topic.