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.