I think my memory is getting worse as well and absorbing information from books is harder. I seem to have a perfect memory for the negative things in life or bad memories and remembering smaller factual details is much more difficult. The only things that I still have excellent memory for are spatial awareness, memory of places on one viewing only, not getting lost, etc. Remembering names, faces and so on if they're not reinforced has always been difficult for me.
I don't exactly know what "brain fog" is, but I see it described a lot on trans forums. I'm not sure sometimes if people mean it makes it hard to concentrate, or interferes with memory, or maybe it's just a tendency to be distracted or not be able to sort out feelings. Until I know what it is exactly I'm not sure if I have it or if I just have a very selective memory and need things to be hammered in.
Few years ago my mum had a brain aneurysm and she developed a few memory issues, as well as dyslexia as a result. This wasn't acceptable in her job so she spent a lot of time doing memory exercises, word games and so on to improve the issues in her memory and kept her job. Far as I know it worked well, so maybe I will start doing some memory exercises and puzzles to help myself in the memory dept. One thing that does help is repetition - I'll watch or read factual stuff several times and that seems to make sure the information stays in longer.