Five SFF worlds tied together by string theory

Ryan Graudin's most recent novel is Invictus. At Tor.com she tagged "five of [her] favorite series that cross multiple dimensions," including:Shades of Magic series by V.E. Schwab

I, like many others, love Schwab’s take on the multiverse. This series features a finite number of worlds, all four connected by a single fixed city. Grey, Red, White and Black… each version of London has its own