Operating Systems: Design and Implementation, the Minix book that is sort of famous for inspiring Linus Torvalds, is more targeted at those who want to move into OS development.

Modern Operating Systems is an amazing book but it works at a somewhat higher level. You'll basically read about stuff that happens, or might happen, in an operating system. You'll learn about threading, the elevator algorithm, dining philosophers, how virtual memory works, how a memory allocator works, and a bunch of other stuff.

It's a very well written textbook. The thing that struck me was the way it introduces things at a theoretical or high level and then trusts students enough to present them with real C code and real problems to solve on the next page. Just an excellent textbook.

It's great. Buy a used paper one. For undergrad purposes an old edition is fine and will be cheap.

I teach OS using MOS, and give this advice to (several hundred by now) students.

I'll disagree with the other reply and say that it is fantastic knowledge to have, no matter if you do OS work or not.

Find a used one, mine costed $7, albeit an older edition.

It's an extraordinarily written textbook. For me there are 2 types of technical books - the ones that I have to plow through with sheer willpower, and the ones that I read kinda like an interesting novel. Tannenbaum's book falls in the latter category.

The book presents OS theory and is more suitable for OS developers.

In my opinion a well rounded developer needs a good understanding of what happens at the OS level, even if he is never going to write a device driver. Tanenbaum's books are excellent for that.