Fredrik said:
It does require more mathematical prequisites than most physics students have.
His functional analysis book is very popular, so he seems to know how to write good books. I'm sure it's fine,
His FA book is ok. But if we're talking about
https://www.amazon.com/dp/0486667219/?tag=pfamazon01-20 (perhaps an expanded version including Riemannian Geometry?), I have to warn OP: this is pretty
old-fashioned! Everything is done in local coordinates, and mostly in three dimensions. Compare this book with something like Lee, and you'll see they are almost disjoint.
but it's hard to beat Lee. Hm, there's also a book by a guy named Manfredo Perdigão do Carmo that's getting good reviews at Amazon.
Lee is pretty good in my opinion, but of course it's not the only one. These all have their merits:
Tu - An Introduction to Manifolds
Spivak - A comprehensive introduction to differential geometry Vol I
Darling - Differential Forms and Connections
Lang - Introduction to Differentiable Manifolds
Conlon - Differentiable Manifolds
Barden, Thomas - An Introduction to Differential Manifolds