Oh heck!!! Chuck the book away!
My ds sleep roughly went like this:
until about 7/8 months went to sleep either by being fed, pushed along in pram, carried hugging my front in sling, leaning on my shoulder being sung to and stroked or tucked up and drift off of own accord. All depended what was going on or needed at the time - he has bad reflux so sling and shoulder were great as upright was better than horizontal!
As he got older he still has sling and pram, but more often put in cot and would often be stroked to sleep or fed.
gradually as his awareness increased he started wanting to be in his cot, though sometimes would still like a stroke or hand to be held.
Can't remember exactly when but around 14 months it was quite normal for him to be popped into his cot for bed or nap and kissed and tucked up and left to it wide awake, he would go to sleep on his own happily.
He is currently 22mo and his nurseries easiest little sleeper as he is the only child who will take himself to his mat, lie down and go to sleep just by being told it is sleeptime. All the other children (so they say) need to be put/taken/sat with or stroked.
For me the success to his sleep is the fact that we haven't had steadfast rules about exactly how he must go to sleep, but instead we have encouraged and facilitated a calm regular sleeptime where he self settles... but first and foremost we have always just responded to his needs.
His needs have differed at different stages of awareness, physical ability, typical pattern etc but at no point have we made an issue of sleeptime, it naturally develops because humans naturally want sleep, so provided a parent isn't creating disruption or anxiety around sleep, and provided you have in your minds eye an eventual goal of self-settle so you can encourage that direction - nothing you are doing now will be spoiling anything.
So much changes between now and the next 3 months and the next 3 etc etc that him being relaxed and happy around nap/sleep times is as much as you need for a successful sleeping baby in future.
HTH
:)