Mintzberg's book is one of those papers that must be read for anyone interested in the drives that shape the organization structure. It's well organized and starts out by the basics as coordination mechanisms and dives into the driving forces (internal and externals) through all the literature available by that time.
Its final explanation of the structure as the outcome of forces and drives shed insight into structure as an outcome (affected even by fashions). This envision is clear even if new forces are uncovered by the experts.
On the drawbacks side, the book is slightly out of date regarding the research background for a nowdays reader(not its fault since the book is 20 years old), some chapters as the impact of some factors in structuring are padded out and the human being behavior impact is lightly treated. Some outlooks have failed (20 aditional years gives you some "foresight" to see why they went wrong, which is funny).
All in all, even if it's slightly outdated, it is worth to have a go at it. It's easy to read and offer a good overview.