I started my trip in Beijing and I was impressed by the detail in the LP guide at first, but then as I started my sight-seeing it became clear that LP exaggerate everything and make a lot more of places than they really are.
This has two problems, firstly you end up going to places in the book that sound very good from the description, but then you arrive and are disappointed. The second problem is that you end up wasting time doing pointless things while missing out on more interesting parts of the country.
The prices are rubbish, simply put they are all out of date and very optimistic. I stayed in plenty of budget hostels and the price quoted in LP is usually 20% too low.
Finally, it is clear from reading the book that the LP writers like to indulge and tell hostels, hotels and restaurants who they are because the levels of service described in the LP for so many places just never materialised for us non LP writers. LP started out as a guide book for backpackers, but it seems like the LP writers are anything but. The whole books is lacking in down to earth advice on travelling and is full of flowery language which honestly just irritates.
Add to that the searches and confiscation trouble at land border crossings into the country and it is hardly worth the trouble.
I would never recommend travelling China without a guidebook as it is easy to get lost in such a huge country where almost no one speaks English, but I would try the Rough guide instead. A couple of friends had that guidebook and it gave much better advice on almost everything, from where to see the best parts of the Great Wall to which parts of China are worth missing.