I read the whole series as a child. The only funny bits I could remember were mostly from the first and second books, with a small smattering of stuff from the third. (Mostly "We apologize for the inconvenience.") Read the later books, and I don't even remember the fourth, while the fifth had a little glimpse of his earlier silliness (the delve into the accounting systems of the HHGttG HQ stands out in my memory) it seemed more like it ended with a giant "FUCK YOU" to everybody who loved the series. Methinks he was writing it because he felt obligated rather than out of any particular love any more.