From my perspective, Sigrid van Dort has a very accessible style of writing combined with a serious scientific-based approached.
On the other hand, I would say her books suffer somewhat from problems concerning spelling and grammar. At least, this goes for her books on "Chicken Extremes" and the...
By far the most helpful book on chicken genetics I use would be
Sigrid van Dort, The Genetics of Chicken Colours
https://www.chickencolours.com/index.php/genetics-of-chicken-colours/
The author offers an incredible amount of details and takes an analytical, scientific approach, while always...