The topic for the book is very interesting & well-motivated (why would an autocratic regime like the PRI in Mexico bother holding elections) & the main thesis (show of strength/popularity) + other supplementary ones (e.g. opposition finds it hard to coordinate both because PAN/PRD have opposite political views and because many 'moderate' voters won't believe accusations of fraud) seem reasonable.
Still, the book suffers quite a bit from an enforced academic style which pushes it to develop and defend overly simplistic theories. For instance, are all voters either "moderate" (will not believe accusations of fraud) or "radical" (always believe the PRI is committing fraud)? Much of the book uses economic-style utility maximization models but these largely seem stylistic. The utility functions are simply lists of priorities for the actors and the resulting analysis is qualitative (e.g. no optimization performed, no general equilibrium discussed...). Agents try to achieve their priorities and minimize the things that hurt them. Duh?
A lot of the empirical results are interesting in terms of correlation but, again, aren't super well-motivated. e.g. probits on voter choice when none of the variables are plausibly exogenous (here meaning do not suffer from omitted variable bias).
BM seems really smart & knowledgeable. I would have liked to see her write a qualitative work using her insights to build a more fleshed-out picture.