Please definitely make that pre-rendering a user option. If you can pre-render
chapters, you can certainly pre-render entire EPUBs – at least as a user
option. iBooks can prerender EPUBs, even showing nicely the number of
real pages (screens) in Table of Contents – therefore, Marvin should definitely accomplish the same, given that it runs on the same devices as iBooks.
Really, calling two entirely different concepts the same name, "page", even simultaneously in the same footer (!), is the most glaring, in-your-face inconsistency in the history of Marvin.
If most users don't care about that inconsistency, OK. But for those of us who do care, please give us the option to treat "pages in book" in the same way as "pages in chapter". Then, cedhax's concern would be "automatically" taken care of as well.