Not how many I've read this year, or will read next year. Because 52 books might get me into March. I'll have read 250 books as of today--and the number is that low because I slacked off at the beginning of the year, and then was rather ill in April. Otherwise, 25 books a month is pretty standard for me if I read every single day.
I use the challenges to diversify my reading. Otherwise, I'd spend all of my time with murder mysteries, East Asian literature, and the occasional literary fiction from everywhere else.
I also keep a reading journal to track what I've read; however, to plot out what I'm reading I use my computer to find the challenges, then start slotting books into the prompts. I have zero hesitation about doubling up on entries across challenges, if necessary; however, most lists will have at least some prompts that are unique to that challenge (read a book by someone with 'Fred' in their name). Hence why I reference so many different challenges.
Once I have the challenges sorted out, I create a master list of the order in which I'll read those books, and the 52 book/week challenge is the anchor for distributing the books from other challenges evenly over the year. After that, I log exactly when I read the book in my reading journal, a Hobonichi Techo planner. If it takes me 2-3 days to read it, I log each day I spend on it in the journal.
Next year, I'll probably construct the list around the ALA Recommended journal list, because it comes out earlier (July v November for 52/52). The only drawback of the ALA list is that they pick the book for the week. That's not a problem for now, since I haven't been the most diverse reader in the past. It might be a problem later. We'll see.