I have read a lot of reference books about the U.S. Presidents and one I particularly like is Our Country's Presidents
, written by Ann Bausum and published by National Geographic Society. While it's chock full of information, it's designed to be easy to use and includes a great many interesting illustrations. I recommend the fourth edition, published in 2013, for ages 10 through teens, and think adults will also find it interesting.
Another intriguing book is Our White House: Looking In Looking Out, a combination of fiction and nonfiction about the White House and the families who lived there. It's a big book, with lots of short entries, and is a good read aloud for younger kids as well as a book that appeals to ages 9-12 and beyond.
(Cover art courtesy of National Geographic Society)