This is a worldview changing book when it comes to both soccer coaching, and child development. This is that influential even after having read or at least tried reading 20+ soccer coaching books, watching 20+ videos, earning coaching licenses through the US Soccer National D course, and playing soccer since I was 6 in the US, France, and Brazil.
There are three things that make this a great book:
1). Understanding children's capacities and needs. I learned how most kids are receiving coaching instruction that does not fit them at all, and so actually hinders them. Like a shoe that does not fit. Often kids are playing with far too many numbers beyond their abilities - such as 6v6, when they have not even shown any mastery at 2v2. So the actual activities in practice and competition need to be tailored to the abilities of the kids for efficient learning and maximum enjoyment.
2). Children learn best by discovering. I learned so much how to not give answers to players where they end up relying on the coach, and not becoming creative problem-solvers. By answering open questions the coach poses and playing simplified games, players learn how to learn: perceive (look), analyze (think), decide (act), perceive the effect of decision (pay attention to result).
Most people think soccer starts developmentally at the feet, and moves up when older to the head as the game becomes more about tactics and teamwork. Actually, soccer starts in the head as every action involves thought, moves to the heart where passion and joy develop from success and expressiveness, and then to the feet where technical skill is developed. This is contrary to many schools of thought that think technique should be taught outside of context to tactics. And this makes no sense as invention (skill) is born from necessity (situation). Just dribbling or kicking the ball for the first time is a process of perceiving, thinking, deciding, and noticing the result. And this learning process will always happen naturally as long as the number of factors is not so great to overwhelm a person or answers are artificially introduced.
Like Horst Wein says, Nature herself is not in a rush, and neither should we be so that everything happens at the right moment.
3). Step-by-step progression. Players need success and new appropriate challenges to remain motivated. Here is a program that is very logical, thorough, and sensitive to the abilities of coaches and players.
For instance, an example practice structure for u7-- 2v2 competition, game for passing/shooting, game for dribbling, game for tackling, back to 2v2 game to see if skills have improved. (Notice everything is a game, as kids want and need to play. Also, notice the pattern of starting with the game, and then taking a step back to learning something simpler which is impeding success in the more complex game, and then back to the complex game to see what improvement is made.)
Seasonal progression from u7-u14:
u7: games for basic abilities (passing/shooting, dribbling, tackling), 2v2 games
u8: u7 content + games for learning 3v3, 3v3 competitions
u9: u8 content (which includes u7 content) + 4v4 competitions
and so on... a nice ladder to move through the complexities of the game
I have personally used these coaching methods for the past 1.5 years after 3 years trying other methods (including US Soccer's and Brazil's coaching methods), and have found them to be more effective and enjoyable for players.