Ironically, most of the better bits, and indeed the overarching plot thread of HPMOR are largely down to the huge gaps in various characters' rational thought. If Harry had made the obvious "let's not trust the sinister guy that's obviously manipulative and definitely more experienced at it than me" leap right at the beginning it might have been a much shorter series.
Apart from young Harry picking up some of the flaws in the organization of Rowling's wizard world in the first couple of chapters in the first few chapters and the combat lesson scenes, there's really not that much rationality going on. Most of the rest of it is characters trying to achieve particular goals whilst being thwarted in large parts by emotional impulses and glaring oversights the reader is positively screaming for them to notice, which is pretty much Fiction 101.
Harry as a character in HPMOR works because he's implausibly precocious, ambitious and devious, which is quite cute in an 11 year old, not because he [sometimes] draws particularly well-reasoned conclusions. We do judge the series on whether we like him being really smart, but that's quite different from him being really rational.
If super-detached and accurate analysis of a situation is what turns you on then I think Arthur Conan Doyle nailed down the "rational fiction" genre with Sherlock Holmes over a century ago.
It's funny how Sherlock Holmes stories were considered very clever at first, then there was a backlash from authors like Agatha Christie who emphasized "realistic" psychology and disliked "magical" deductions from surface facts, and then it turned out that Conan Doyle's approach was right after all, because his stories predicted most of modern forensics. That's quite a high bar for future writers of rational fiction!
A general failing of HPMOR and most 'rational' fiction is they suffer from the same plot railroading. Instead of starting with a world rules, characters, problem, and unbiased evaluation of what happens they generally try and fast talk their way into some predefined plot.
In the short term this can work, but for longer plots you still need to whack ever increasing numbers of people with the stupid stick or backtrack and edit in a few plot relevant items at the beginning ex: The Martian.
Apart from young Harry picking up some of the flaws in the organization of Rowling's wizard world in the first couple of chapters in the first few chapters and the combat lesson scenes, there's really not that much rationality going on. Most of the rest of it is characters trying to achieve particular goals whilst being thwarted in large parts by emotional impulses and glaring oversights the reader is positively screaming for them to notice, which is pretty much Fiction 101.
Harry as a character in HPMOR works because he's implausibly precocious, ambitious and devious, which is quite cute in an 11 year old, not because he [sometimes] draws particularly well-reasoned conclusions. We do judge the series on whether we like him being really smart, but that's quite different from him being really rational.
If super-detached and accurate analysis of a situation is what turns you on then I think Arthur Conan Doyle nailed down the "rational fiction" genre with Sherlock Holmes over a century ago.