I've found a few ways to manage chapter-level reading lists. For material that was already up at the old site, the chapters transferred over. For these, I use the old site's reading list and keep it up to date with where I'm reading/reviewing using the new site.
If you use only inline reviews on the new site, those are displayed on the Inline Posted tab (click the drop-down menu, select Reviews, and then the tab), which are chronological in order, most recent reviews first. From these you can see where you left off.
If neither of these applies to you, then you probably need to keep a paper list or spreadsheet for now. I would think the spreadsheet is easier to maintain, and it works regardless of what you're reviewing and what types of reviews you do.
If Sol can get the sort order of posted regular reviews to be chronological soon, you can use the Regular Posted and Inline Posted tabs to view all of your recent reviews so you know where to pick up with all books you're reviewing. At that point the manual lists are probably unnecessary.
Hope this helps.
Dirk