きまぐれロボット

Very good candidate for your first “novel” in Japanese. The chapters are short, don't depend on each other, and written in a very clear, straightforward, simple style.

Furthermore, the vocabulary is quite restricted and repeated very often... perhaps too often. It was getting quite repetitive by the end of the book which diminished my entertainment rating. The repetition in the structure, setup, and lexical fields of the stories is the part of why it is so approachable for beginners though.

I also liked being able to test my comprehension by checking if I understood the twist/punchline, because there were times where I felt like I understood the words but I didn't get the twist until I re-read a few key parts.

Would I have read this book in my native language? No, but it is very good for language learning.