I picked up the first Saikyou Mahoushi no Inton Keikaku novel despite earlier misgivings on a whim and… ended up suitably disappointed. Things starts out okayish in the first half mostly due to it not being quite clear whether or not the tropes are meant to be satire, but by the third quarter it becomes apparent the story is being told in earnest. The spontaneous harem is one thing, but the contrived setting (there would be zero danger of the shield failing if they just stopped expanding) combined with the protagonist instantly caving to every imposition despite being demonstrably all-powerful is just too much to put up with.
Based on the disappointment of its prequel, I went into the final Mushoku Tensei novel with fairly low expectations. So imagine my surprise when it turned out to be fantastic. Just a beautifully done combination of final battle, epilogue, and overall summation of the series. Zero complaints.