If you want to grow an interesting, tasty and colourful mix of salad leaves, surpassing anything that the supermarket sells, then you need to buy this book. I say this for two reasons: firstly, I know of no alternative book on this subject that comes anywhere close, and secondly, a lot of the advice is difficult to work out for yourself. The book will save you years of careful observation and trial-and-error.
I started growing vegetables a few years back and decided to put a bit more effort into producing salad leaves. With the fancy bags of leaves available in the supermarket all year round it's not enough to dish up a few Icebergs and maybe a bit of Rocket (if the Flea Beetle doesn't get it first that is). My family were turning their collective nose up at my efforts and I needed to up my game. I started looking at the supermarket bags and noticed that they contained many different leaves, Rocket, Frisee (actually a variety of Endive), Chicory, Chard, Mustard, Mizuna, Chinese Leaves, Watercress, Pea shoots, Corn salad etc. and yes, some Lettuce. Charles tells you how to grow all of these and more: which leaves and varieties to grow, tips on where to buy the seeds, when to sow them and how to harvest. Much of the detail is important but not obvious, such as avoiding sowing Rocket at certain times of year to avoid the Flea Beetle, despite what the seed packet says, and not scything plants down in the oft-advocated cut-and-come-again style but carefully picking leaves thus dramatically extending the life and and enhancing the productivity of plants.
I've been growing leaves for a year now, following Charles' advice, and the results have exceeded expectations. I'm very pleased with the taste and range of the leaves I am producing, far surpassing those of the supermarket which seem boring and bland tasting in comparison.
The book does have the usual Charles Dowding' Organic and No-dig aspects (see Organic Gardening: The Natural No-dig Way), but they are only a small part of this book and so if they are not your cup of Tea then there's still lots to learn in book.
Charles grows vegetables professionally and sells to local shops and restaurants. Salad leaf bags make up a large part of that and he's been doing it for years. It really does feel like he's put all that experience into this book.