Maybe the most striking bit of its exploration of the morality of war is that the series spends something like 45 books building up the alien Andalites as beneficent do-gooders who the team of protagonists expect to swoop in and fix everything (including one of the protagonists who is a young Andalite stranded on Earth), and then it turns out that they've been as morally worn down by the ongoing interstellar war as the protagonists have in their guerrilla conflicts on Earth and are effectively as hostile to humans as the original invaders.

> If you must you could probably get away with reading the first ten, last ten

Not sure that you can. If you were to skip any, probably only 31 through 39 are completely skippable, maybe some of the late 20s but I would still read 29 and 30 at a minimum. Some of the teens and 20s might be skippable after 13 but there’s a fair amount of world-building outside the Chronicles series in the 20s; and 40 onwards is setting up the end game and then the end game. 41 and 48 are both weird but also kind of key towards finalizing the characters of the two cover characters in the end game.

EDIT: actually 33 and 38 shouldn’t be skipped either. They’re Tobias and Ax books and there’s so few of those that they’re all kind of essential, but maybe the Tobias books just a little bit more essential.