I was failing badly in my computer architecture courses. Received a 5% score in one of the mid-terms. Switched from the recommended book to Andrew's book and did nothing apart from read it everyday for 2 hours. Received 100% in the final. Such an amazingly approachable book. :-)
Out of curiosity, which was the recommended book?
One if my favourite books on computers and looking at the comments, many people here too.
Source: this book got me top marks too