Joel Spolsky tells a good story. His narrative style is easy to read, and almost every chapter in this, his fourth book, is enjoyable and entertaining. The book is subtitled:
Further Thoughts on Diverse and Occasionally Related Matters That Will Prove of Interest to Software Developers, Designers, and Managers, and Those Who, Whether by Good Fortune or Ill Luck, Work with Them in Some Capacity.Which is mostly a good description, with one caveat - Joel hardly touches on the actual nitty gritty of programming at all. Which is probably a good thing. You see, Joel is mostly a manager, his book is written from that perspective and for programming professionals, this is a useful viewpoint to learn about; you can be the most brilliant technical programmer in the world, but if you don't understand the business needs of your organization you might as well be an enthusiastic intern.
While I mostly enjoyed the book (or "blook", since it is really a 'best of' compilation of articles from his blog in hard copy form) it should be noted that it at times feels like reading an extended advert for Fog Creak Software (both for the software they develop, and as a not so subtle recruitment drive).
In conclusion, More Joel on Software is an enjoyable book, of interest to professional programmers, about the industry they work in. If you are mostly programming, it is not the kind of book you will be referring back to frequently (though it might be the kind of book you quote when advising management, or becoming one yourself). If you're not already familiar with Joel's writing, it may be a good idea to visit his blog first, and try before you buy.