I've been on a bit of an alternate history kick recently. I can recommend both Scott Westerfeld's Leviathan-Behemoth-Goliath young adult steampunk v. biotech alternate World War One trilogy, and Ian Tregillis' Bitter Seeds-The Coldest War-Necessary Evil demonologists v. bioengineered ubermenchen series. (Neither is rationalist fiction in the sense of having super rational characters, but it is realist fiction in the sense of character's making mistakes for bias-related reasons.)

Also, I seem to recall seeing Yvain say something on his blog recently about being surprised that many of the people he knew who reference Lovecraft haven't actually read him. For those who aren't aware of it, all of Lovecraft's solo-authored work in chronological order is available as a free e-book here.