This is a very good value book for the multiple choice element of the test (although I thought one or two of the questions were needlessly ambiguous). The real reason for my 4* rating, not a 5, is that the advice on grammar at the end of the book is seriously wrong on at least two points, and contains several errors of punctuation and syntax itself, which slightly discredits the book. Personally, I doubt whether anyone who needs such basic advice on grammar would do well reading law at a top university anyway.
Preparing with this or similar books doesn't guarantee success; and a high score on the LNAT won't get you into a good university by itself. It shouldn't do you any harm if you use this book sensibly, however, and it might help you practise your technique and thus gain confidence. (I achieved a well-above average mark and got a place at my first choice university.)