Warhorse was a children's book but now it is a play. We went to see it as our first Christmas not-a-panto this year; and that made sense. TL;DR: good.
It is all rather well done. As everyone says, they horse puppets work well despite there being no attempt to hide the puppeteers; the bird puppets sort-of work too: well, the little flying-joyously ones do, and maybe the crows. I'm less sure about the comedy goose. Another bit that works well is the shooting, which is sudden and startling, rather than slow. The tank towards the end is odd; that didn't seem to make sense at the time. Looking now at the wiki page about the book, I think that's how Joey gets stuck on the wire, but that wasn't really clear in the play.
The only bit that sticks out as implausible - other than the inevitable co-incidences, which aren't too blatant - is Friedrich the German artillery officer practically doing a "lumberjack" and saying "I didn't want to be a soldier".
But what do we make of it on the moral or intellectual plane? It ticks all the obvious boxes: war is bad, hard work and perseverance is good, drunkenness is bad (errm, even if it has good consequences, never mind that), and so on. But we knew all that anyway, so that doesn't get you much. Does it provide any kind of insight? Does telling WWI from the viewpoint of a horse bring anything fresh and new? No.
