There are two issues here: are you allowed to study just from books, and is it actually possible to pass the exams by doing so.
I don't know the answer to the first question. I know that there are exemptions under some circumstances, but I don't know what they are. Have a look in LASORS, and if that doesn't help then contact the CAA (or alternatively, any reputable groundschool should know the answer).
As for the second question, my advice would be don't even try it. I really don't think it's possible. The exams are there to catch you out, and it doesn't matter how much knowledge you have, if you haven't had anyone point out the tricks to you, you will fall for them.
A couple of examples: the Jeppesen pack that you use contains two versions of one particular airways chart - one is a genuine chart, albeit quite a few years out of date. The other is produced specifically for the exams. They cover the same area, but they are different - and if you don't realise that (or have someone point it out to you at groundschool), you won't be able to answer the questions which are based on it.
Or there was the Air Law feedback question which I learnt the answer to, and was very pleased when it came up on another feedback paper and I remembered the answer from the previous time. Surprised when I marked the paper and found that I'd got that question wrong. It was only very close examination that I realised that one question was about JAR regulations, the other about ICAO, but that the two questions were otherwise identical.
This is the type of thing you can, IMHO, only find out about on an approved course. Do a distance learning course, attend the brush-up, and learn the tricks of the trade.
Good luck!
FFF
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