“The Return of the Time Machine” by Egon Friedel (german title “Die Rückkehr der Zeitmaschine”, I doubt it’s actually been translated).
The only redeeming quality is that I paid only 2€ for it, but even that feels a bit high.
It’s a series of fictional letters between Wells and Friedel, with the latter aggressively misunderstanding the original book and physics. That’s all I remember, I don’t think I finished reading it, but it’s probably still in a box somewhere
Terry Pratchett’s “Nation” is also technically a Young Adult novel, so it’s not that reliable as an indicator of bad writing.
(Nation is fantastic by the way)