SOLVED. Adult Fantasy book about a magical land where tools and technology get better with time/ use. [s]

[Ondrej]

I read this book ages ago and would like to suggest this to my son but can't remember the book title or author anymore.

What I do remember is that a boy from the "real world" somehow gets transported into a fantasy land. There he starts building tools. Those tools a at first of a very poor quality but as time progresses they get better. In the beginning he first thinks that he got better at using them and that's why they appear better but later in the book he realises that they actually do get better. Even later he learns that some kind of "energy" from the user of the machine is transferred during the usage of the tool and that's how they get better. At one point in the book he builds a vehicle out of a tree log (i think) that over time becomes sleek and quick and ultimately becomes a flying machine.
(It's possible that this is not a single book but a book series)

[Sue]

The Practice Effect by David Brin.

[Ondrej]

Yes! that's it. Thank you very much!

[Kris]

Glad you found your book, Ondrej. Here's the link for Sue's find - The Practice Effect by David Brin.