Right, black box testing and exploration testing are the most interesting, it can be like a game. Detective work where good analysis and diagnostics skills are required.
When you find a failure, you have to investigate further to pin point the defect, to have something tangible and accurate to report to the developers (so that they have no other choice than to believe you ;-).
You're not the guy who made the code, but as a developer yourself, you know how it works, and you know where developers sometimes neglet to shield their code or what is likely to fail. You don't see what's inside that "box", but you guess. You have a totally different point of view than the coders who made it, so you see things they don't see.
It can even happen that you end up explaining them how what they wrote works, that you gain a better understanding of what their software does in reality! Think networking for example: with modern high level OO languages, networking is completely burried into many software layers. Opening a remote connection at high level is easy-peasy nowadays, but many programmers (especially youngest ones) don't know (or are not interested to know) what's going on down there on the cable. Your tool will be Wireshark and with it you'll see the live connection, you'll see in details how it works or fails, not how the developer expected it would work.
Software testing can be much more than pressing buttons and ticking PASS/FAIL checkboxes. It's a domain where you can have plenty of freedom and can use all your imagination and skills. Some tasks such as preparing test cases or writing reports can be boring but it's not worse that documenting code for a developer. Some coders will see you as a fellow who helps them while some others with a large ego might not like you very much, especially when they cause many defects and see your name too often! But being a good tester is rewarding. If you can share this job with some programming, you'll be a happy guy.
A book I recommend is "Lessons Learned in Software Testing": http://tinyurl.com/86f9q48