It really depends on your goal. If you just want to be able to read the typical inscriptions you'll find in a museum (e.g. offering formulas), Collier and Manley's book is pretty decent.

If you want to dive into Middle Egyptian literature, and especially if you have any interest in learning other phases of Egyptian, you'll probably want to seek out a more detailed introduction. There's several good teaching grammars out there; I was taught Egyptian with a combination of Allen's Middle Egyptian and Hoch's Middle Egyptian Grammar, with a bit of Depuydt's Fundamentals of Egyptian Grammar dashed into the mix. I prefer Hoch's organization and presentation of grammar, but Allen's book is better for self-learners, I think.

There's a very good discussion of Middle Egyptian resources here.