5 without a doubt
for the entire saga (to be read in one go).
I believe it has extremely intelligent humor, (in a sense also philosophical).
I found the movie disappointing, but it was hard to do justice to the genius that emerged from these stories in a film.
The review, well no offense
wasn't bad, but you limited yourself to citing a few gems and commenting on them.
A story that starts from the fundamental answer (without having the question),
and ends with
the Message of God to all the inhabitants of the universe; perhaps a book like this deserved more analysis.
So much so that it leaves no room for those who have only seen the film and think that the book is just a more beautiful comic fantasy than the movie.
I've followed the literary controversy on the admissible comparisons with Pirandello.
Here's my take:
Adams contains as much as Pirandello, Kundera, or whoever you want,
it doesn’t matter if he uses humor; it depends on what one can read in his paradoxes.
Personally, I find him somewhat similar to Bunuel; he used humor to destroy bourgeois conventions, and Adams does the same, with the same ferocity, against beliefs, dogmas, and absolutistic and universal convictions.
To stay within literature,
perhaps the most immediate comparison is 'Venus on the Half Shell' by Farmer,
another must-read book, also comparable to people like Pirandello, Manzoni, or what do I know... Torquato Tasso (and Pier Capponi?).