[DeepL Translation - needs review] Volume 1 Introduction: As a working adult, Kazuhiro Kitase's only hobby is to sleep anyway. Ever since he was a child, he has been having exciting adventures in the mysterious dream world he always sees. One day, while adventuring with an elf he befriended in a dream, they were unluckily burned together by a dragon's breath. When he wakes up from his dream, he finds a young elf girl sleeping peacefully.
(Translator: DeepL)
I really like this series as a manga and I've been eager to read the original light novel to see if I can handle it. The good news is I can, with major technological assistance. I'm not in a great position to evaluate it from a literary perspective (though the English translation was a bit flat, which I now realise was probably accurate to the original Japanese), but it is quite a good book for learning - when you get bored of the IRL stuff you jump over to more fantasy stuff which has more difficult vocabulary but is generally more action-packed and straightforward as a result, at least in this volume.
The narrator has particular turns of phrase and descriptors that he turns back to time and time again so it's a good read in the sense you'll see a lot of vocabulary repeated in similar context. I probably wouldn't read it unless the LN-ish premise appeals to you, but it does to me and so I quite enjoyed it.