Just finished this. Really enjoyed it. Kept expecting it to drop off in quality or start to get grating, but surprisingly it stayed solid.
Contrary to views expressed above, I felt it did a great job of presenting irrationality in a way that was mostly easy to follow.
It’s been 20 years since I read the books, so can’t remember, but I feel like the tv series is only very, very loosely based on them — as in, they both feature a character called Dirk Gently. Really, the only things I can remember from the novels is a guy on a horse for whom everything appears to be the exact same shade of pink, and the bill issued by Dirk Gently for saving a cat.