Learning About Maths

So I am about to finish a Batchelor of the Arts degree, which turned out to be an absolutely horrific mistake. As some kind of weird reaction to my educational experiences I have become fascinated by mathematics.

I have always had a passing interest in maths, despite the fact it was something I dropped in school at the earliest opportunity, but recently I've began investigating it a bit more thoroughly.

I have bought myself this maths textbook:

...which I have been happily working through (from the very beginning), and I also bought a book about the Reimann Hypothesis by John Derbyshire. This book has piqued my interest, and it is very well written for those with little mathematical knowledge. I've found myself able to absorb information about calculus fairly well, considering it wasn't something featured on my GCSE syllabus.

I am not 100% sure where this interest is leading - I've talked with a colleague about studying together at an evening course for an A-Level next academic year, but I am worried it will crush my budding interest.

Basically, I am wondering whether any of you lot could recommend me some other textbooks/mathematical texts, and general maths-related advice.

The reason i dropped it at school was because I didn't seem to be 'good' at it. I was surprised when i got an A at GCSE, to put it mildly, but it confirmed my suspicion that I wasn't 'bad' at it, but rather just took a fair bit longer than my fellow students to work things out. I did see some texts about how to speed up mental processing when i bought my textbook - any advice from you forum types would also be much appreciated.

Thanks for reading my little maths story - looking forward to (hopefully) getting some responses.