Currently I have been studying a book by Nicholas Rescher titled Rationality - interestingly he treats 'reason' and 'rationality' as interchangeable for the general case.
Nonetheless, I find his theme of rationality being normative or didactic, i.e., showing us what we should do, worrying. That for two reasons: Already in the 20th century critics like Theodor Adorno pointed out that rationality can easily be turned authoritarian by 'rational' organization, whilst we now find many people revolt against any suggestion of dictation, even from health advice. The other, related, point is that in many situations (the Middle East being the outstanding example) we have to deal with people who simply ignore norm(s) of rationality.
Rescher's best point (p. 221 of Rationality) is that any critics of reason/rationality still find themselves needing to use it for showing what its limits are. (Adorno was well aware that rationality is needed, but also of how easily it can be abandoned). I hope that my little ebook (Ethics and Survival) might encourage more people to think about getting rationality and emotions working together, instead of being in separate compartments, as the one time Scottish philosopher John Macmurray suggested. I am not sure I accept Rescher's claim that rationality is a specifically human evolutionary heritage, but I would say it's survival value has risen exponentially with the (destructive) power of technology. For that reason, it neds to work with emotions, not least fear. Connecting rationality with emotions should help to link it with more elemental norms like it being wrong to kill people except in self-defence.