I don't believe in the books.
I did it this year, and in the practise tests (the official ones on the LNAT website), I got 29/42 - which is an amazing score.
And one would think one would expect a similar score, due to the difficulty supposedly being the same, but no, the excerpts of texts I had in the test were incomprehensible to me - and that's even when I took into account SLIGHT exam pressure.
I got 18.
Still got into Warwick - so it worked out pretty damn good.
So, just read some broadsheet newspapers, do the practise tests on the LNAT website and hope to God you don't get unlucky.
Good luck.