The Future of Another Timeline

I have always been a sucker for clever time travel stories, and this is one such. The premise is very novel: time travel nodes from the Ordovician era?? And having a to-and-fro jump every chapter between an older and a younger protagonist, and having a rather surprising revelation as to who they are - clever.

The book goes into a fair bit of detail discussing theories of time editing, and the protagonists attempt to do a fair bit of their own, and it is all worthy, and Good...and then you think about it a bit, and the absurdities jump out and bite you, and you think "What, really? Historical eras carry on, with time machines embedded in them, with travellers arriving from the future AND NOT INFLUENCING SOCIETY?

Hmmmmm... nope, doesn't work. But SF is about willing suspension of disbelief, and I've disbelieved bigger things, so - I liked it.