As a follow on to this question, what books would you like to see retranslated or rewritten as the original translation wasn't very good, or can you give examples of books that have been translated more than once into the same language.
I nominate Felix Klein's Lectures on the Icosahedron and the Solution of Equations of the Fifth Degree as a book that deserves retranslation. The present English translation was made in 1888, and it contains a lot of archaic terminology, such as "permutable" for "commuting," "transformation" for "conjugation," and "associates" for "conjugates." Also confusing, though in principle a good idea, a normal subgroup is called "self-conjugate."
Best of all, a new edition would give an opportunity to introduce some pictures, which are incredibly absent from Klein's original text.