I'm having trouble understanding ところだったりする in this sentence. From what I know ところ can mean 'place, spot, area etc.', 'just about to do something' or describe a state when modified by another word. たりする is usually used to list inexhaustive example.
With just these definitions it doesn't seem to make sense to me, so I searched around for だったりする and found that it could mean 'to happen to be' (from this question here) or 'probably'.
I think it's likely to mean something like this: "By the way, right now I'm at volume 23 and after this (it happens to be / it's probably) a good spot." but I'm really not sure about that.
For more context this was said previously: "全３０巻もある漫画を読んで、つい徹夜をしてしまったってことか。"