I'm interested in philosophically digging as deep as possible. I'm looking for a book whose subject is to speak about the ultimate foundation. I apologise for this scarce description, the topic I'm interested in seems almost indescribable. The only sign of such a book that I can think of would be that things get really weird at the foundation. For example: I once had an idea to write a book whose syntax would be self-explanatory, as to avoid the meta-language regress, but I have no idea how to do it.
Using symbolic logic in philosophy is close to my heart, but that's not a necessary requirement for the book I'm looking for.
Thank you for your suggestions, God bless.