What worked for me was first to understand what they are good for, and only after read the mathematic fireworks. I always liked [1]. I think Ganter also offered copies of the main reference book by personal request. I find nice that with FCA and given a bag of triplets saying what entities have what attributes (only one fixed predicate, varying subject and object), FCA discovers the best T-Box (concept hierarchy) to organize them.

[1] http://www.math.tu-dresden.de/~ganter/psfiles/FingerExercises.pdf