These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Cat Who Walks Through Walls
Fair for Its Day: Some of the dialogue between men and women can read as incredibly chauvinistic, but this has to do with the time period the books were written in. YMMV very much on whether or not Heinlein was actually purposefully sexist.
Thirty Sue Pile Up: When all the characters from Heinlein's other books wind up in the same room together. If you aren't familiar with his previous work, good luck even telling all the charmingly arrogant libertarian supergenius horndogs apart without a scorecard. Some of them are even clones of each other!