Some time ago, I read a library book that had three short Heinlein novels: Puppet Masters, Waldo, and Magic Inc.
Puppet Masters was good sci-fi, and one of the best Heinlein books I have read. It is a fun and fast-paced story of alien invasion. There was one glaring plot hole, however. The society has a recreational drug that vasty slows down the human perception of time, allowing one to experience a lot more ina short period of time. As written, people who are on the drug actually move much faster than normal. However, despite the obvious possibilities, this drug is never used for working, combat, missions, or any practical reasons. The reason why the speed-drug is unsuitable for anything other than recreation is never given. This trhing is annoying, because it shows that the author hasn;t really thought about the world. It is just lazy writing.
Waldo was interesting but disappointing, mainly because the plot ends up relying on mysticism. I don't mind when a story is about mysticism and fantasy right from the start, but Heinlein has a bad habit of pulling a bait-and-switch where a sci-fi story turns into a fantasy story halfway through. I also think that this is lazy writing. I also didn't like what happened to the main character. he started as an interesting, well-rounded character, but at the end of the story he had 'cured' himself and turned into a nobody who was not doing anything useful for humanity.
Magic Inc was fun. Magic is part of the plot right from the start, and it talks about all the ways that this would affect society. It spent a little too much time tlaking politics, but was a good story overall.