RE: I'm a tenured philosophy professor
Hey @bitcalm, good question. Yeah a lot of philosophy - even historically - is written for other philosophers, where it's assumed that they know the relevant background. This makes sense from a certain perspective; compare academic work in other fields. If a chemist had to start a paper by explaining every concept in the background, it would be page 1,000 before she got to start explaining her own result.
But of course this does not make it easy for someone who wants to start learning more introductory stuff. The trick (as in chemistry and other fields, and even on Steemit!) is to start with the right readings and teachers. I might recommend Bertrand Russell's famous The Problems of Philosophy, which is an intro book that recently came into public domain! I have other ideas & resources if you can give me a more specific idea of your interests.
Thanks, I'll take a look at that book.
As for my specific interests? That's a good question. As a person I have a strong belief in fairness, equality, and justice. I also think topics like "what do you need to be happy?", "what defines success?" also interesting. So I suppose those are good places to start.
For "fairness, equality, and justice", you can't go wrong with John Rawls' seminal Theory of Justice (which is not public domain, though Rawls probably would have made it so if he reasonably could have in his day). This book incidentally provides a powerful counterpoint to libertarianism, if you happen to lean in that direction.
There's also this free online course at Harvard. I haven't seen it myself, but I hear it's very good, and the teacher is a big name among us philosophers.
I just realized I never answered your question about philosophy on "what do you need to be happy?"! This understandably may be of higher priority for you. I'm sadly not an expert here, but I would say on this question the classic (and free!) place to start is Aristotle's Nicomachean Ethics.