One of the first series I've ever read was about a young boy who was learning to become a mage. In this world it was possible to summon demons of different categories, ranging from small and not very powerful Fairy-like creatures, to Gargoyle-like mid-powerful creatures up to giant monsters devouring everything in sight.
What made this series special was the way it was written. Whenever the demon, who was summoned by the young boy, was narrating the story he used cynical annotations about the current situation.1 It was very funny and the in-character reason for providing the annotations was that the puny human readers wouldn't be able to understand the grand way in which he was thinking about everything at the same time.2 Therefore he provided the reader with annotations to make it "easier" to follow his line of thinking.
I absolutely loved the humor. The story itself was about having to steal certain items from more powerful wizards and trying to escape the problems that arose from these acts I think. With each book a few years passed and in the last one he was working in some sort of agency, not really a "young boy" anymore.
There were three books in the series and one prologue book that I've read. I remember that one of the catch-phrases or signature spells or things like that, which the demon used regularly was introduced in the prologue book. A funny thing because of how he always tried to emphasize how much of a genius and how original in his thinking he was.
I've read the books in German. The title contained the name of the demon, something like "[name here] and the [item to be stolen]".
Other random things I remember:
- the demon was always trying not to get into any trouble
- he loved to send weaker demons into the fight and wait for everything to settle down
- the wizards had to be extremely careful when telling the demons what to do so as not to give them a chance to misinterpret the intent
- no intonations
- no breathing in and thereby pausing
- there were a dozen categories for the demons, each one with a different name
Can you help me remember which series this is?
1 [Insert funny text here as an example.]
2 Magical creatures are just better at everything.