An absolute pearl of a book
Stephen Fry Elegant, surreal and philosophically questioning, each story from neuroscientist Eagleman offers an inventive, thought-provoking blend of science and romance

Metro

Sum is terrific. The inventiveness, the clarity and wit of the prose, the calm air of moral understanding that pervades the whole thing, add up to something completly original.
Philip Pullman This stunningly original book is little more than 100 pages long. You can get through it in an hour, but you'd be mad to hurry, and you will certainly want to return to it many times . . . Sum has the unaccountable, jaw-dropping quality of genius. It seems exquisitely adapted to fill the contemporary longing for a kind of secular holy book.
Geoff Dyer

Observer

Anything that tells us, convincingly, that this really may be the best of all possible worlds has something big going for it.

Guardian

Wacky and whimsical; a little goes a long way.
Sue Arnold

The Guardian