Much less airbrushed than the usual NASA fare. The high level politicing and obstructionism and lack of consistency is more or less laid bare to see. The least but clearest of which is this amazing quote from the PI --

We more or less created a ridiculous homework assignment for them, probably months of work, but we only gave them a month to do it. When the deadline came a month later, of course the information we asked for was not complete, and we used every incomplete item as a reason to send them back with even more homework: define this better, finish that in more detail, et cetera.… We basically kept them in the mode of never being ready to design that electric stage we didn’t need.

Doesn't go very deep on technical detail, nothing like the Mars and Me blog's detail on the day to day of driving Spirit and Opportunity, but it does give a good sense of how much was developed on the fly after launch. Particularly striking was not having found a Kuiper belt object for the secondary mission goal until it almost arrived at Pluto, and NASA almost not allocating Hubble time to find one.