Obviously, this is the book tie-in with the Jamie at Home series seen in the UK on Channel 4 and on the Food Network in North America. And for a tie-in, it's actually pretty good.
It's certainly a much better read than his previous Cook with Jamie, mainly because with this one he's made a better attempt at identifying his audience. Jamie, it's obvious, is enthusiastic about his cooking, and he expects his readers to have the same enthusiasm (and therefore the same knowledge) that he does. This is something that was missing from his previous effort.
The book is arranged in a seasonal theme, with recipes for spring, summer, fall and winter. This is good, because it encourages the type of varietal eating that keeps a diet from getting monotonous.
Where the book differs from his previous efforts is the way he talks about his garden. Most of the ingredients he uses are grown from there, with the main exception of poultry and game meats. (The poultry and eggs chapters have an especial interest, given his current project dealing with the exposure of battery hens.)
The recipes themselves are clear and well written, to the point where a high-schooler would feel brave enough about attempting some of them.
About the only thing missing is a chapter on herbs and spices. Oliver uses so many in his dishes you'd think he'd devote at least one page to their cultivation, but he doesn't. Still, don't let that spoil what's probably Oliver's most accessible cookbook to date.