We haven't finished yet since our sessions are so far apart, but my players are knocking out a book every 3-4 play sessions. So, it'll probably be 20 sessions by the time we're done.
Even just narratively faster. You aren't besieging a dungeon for seven days and seven nights. You're breaking into the bad guys base and blasting your way out in under an hour.
I think my PCs went through book 4 in two in game days. A full level of xp in a day of adventuring, twice in a row is very fast.