Think of a great sequel movie. Terminator 2 comes to mind. The original wasn't great, was it? Now think of a great movie with a really disappointing sequel. The Matrix is the one that most people remember in that category - the original was so good that the sequel could only be a let down.
Joel on Software is the best single book on software development I've read. Every developer I've hired has read it, and every one of them has agreed that it's a great book. It is a book of useful tips and simple strategies for building software that works. I could go on for pages describing how brilliant it is; honestly, just go and buy it.
Unfortunately, there's a sequel - More Joel on Software. As soon as I saw it I thought "wow - another 300 pages of invaluable advice that I'll be able to use". Probably in the same way you thought "wow - another matrix movie that will blow me away". Anyway, I've just finished reading it - there are several chapters which were useful to read, several which were padding the book out to 300 pages, and lots which I read and don't remember.
So, at the end of the book I'm filled with disappointment. The problem isn't that the second book is rubbish; it's not. It's that the first one was so brilliant, and the second one was a bit ho-hum. I was prepared to be blown away all over again, but instead I just learnt bits and pieces, just like many other books.
By the way, I never did go to see "The Matrix Reloaded", nor did I bother with the third one, mainly because friends told me it was nowhere near as good as the first. So, as your friend I highly recommend you buy the first Joel on Software book. It's brilliant.