There’s nothing rational about it: Like pi itself, the list of books about pi goes on forever. Here’s a selection of titles that we’ve calculated you might be interested in today:

Easy as Pi: The Countless Ways We Use Numbers Every Day, by Jamie Buchan. Among the entertaining anecdotes in this collection is the story of an amateur mathematician named Edwin Goodwin who, in 1897, tried —  unsuccessfully — to get the State of Indiana to recognize his method of “squaring the circle.”

Pi: Unleashed, by Jorg Arndt and Christoph Haenel. Two German writers summarize the various ways mathematicians and computer scientists are calculating and using pi. An included CD contains — among other things — 400 million digits of pi, which, of course, is just the beginning!

The Joy of Pi, by David Blatner. A jaunty history of our long fascination with pi, from the ancients to the most modern computer scientists.

Pi: A Biography of the World’s Most Mysterious Number, by Alfred S. Posamentier and Ingmar Lehmann. A tour of the long history of pi with quirky anecdotes about how pi has been used and how people have tried to explain its mysteries.

A History of Pi, by Petr Beckmann. A Czech engineer who moved to Colorado writes about how mathematics and humanity progressed together — or didn’t.

The Pleasures of Pi,e and Other Interesting Numbers, by Y.E.O. Adrian. Billed as a collection of essays for the non-mathematician, but before you know it, he’s slipping in some equations you haven’t confronted since high school calc. (The horror! The horror!)

Sir Cumference and the Dragon Of Pi, by Cindy Neuschwander, illustrated by Wayne Geehan. This picture book — part of a clever series of math books — introduces readers six and up to the wonders of circles.

Pi, by Scott Hemphill. Complete truth in advertising here: This free e-book is pi — or at least a good chunk of it. Scott Hemphill from CalTech spent three days computing more than 1.25 million digits of pi using Borwein’s method. Which is not as simple as pie:

P.S. Yann Martel’s “Life of Pi,” originally published in 2001, is still No. 9 on The Washington Post bestseller list.