Covers little more than may be searched for free on the internet. However, does have the research done for you and grouped in a convenient format. If you prefer a book to hand its for you. Personally did not feel worth the money for me.
I quite like handy booklets you can flick through - if you dine out a fair bit you can't be so short of cash you can't afford a fiver for this. So why the low one star rating? The biggest problem with this is that it focuses way too much on the inner city. The outer London centres such as Sutton and Kingston often have a great array of eateries, which this book ignores in favour of inferior restaurants nearer the centre. London has 32 boroughs, not 20. Time Out will always fail partially until it finally wakes up to this fact.
PS I've admired and supported Time Out for decades, but it needs to cover London properly or I'll finally give up on it.