>>4403968>>4404007The original anime only got 2 seasons; I don't remember if they were caught up to the source material at the time but a lot of LN/manga adaptations are just there to advertise the books and simply don't intend to adapt the full series. It also skipped over a book.
The more recent show got created due to a combination of fan demand for a continuation and some really intense work on the author's behalf getting investors and the like, plus general interest in Spring Log and W&P. It appears to be a 1:1 adaptation covering each book, starting from the very beginning.
Both shows are worth watching in my opinion, but I think I like the original's OST a bit more (especially the OP and ED) and Holo's not dfc in the new show like she should be.