If you have a good grasp of multivariable calculus and want to learn differential geometry, I can't recommend highly enough a book that isn't on this list, Loring Tu's Introduction to Manifolds.
I'd tried a few well-regarded diff geo books (Isham's Modern Differential Geometry, Morita's Geometry of Forms, Schutz's Geometrical Methods) but always got to a stage where there was some lack of clarity, something seemed assumed that wasn't explicitly mentioned, or just inscrutable notation that didn't seem to have been explained previously. In contrast, Tu's book is smooth and pellucid in its clarity. Very enjoyable