Not heard of this, is it a book?
It is a book, yes. The No Cry Sleep Solution (NCSS) is a very, very gentle, kind method to help a parent who might be breastfeeding to sleep, maybe co-sleeping too to help the child slowly learn to sleep independently.
One of the central premises the book gets across is to set realistic expectations. That this will take a long, long time of gradual, slow, small changes. That baby may be breastfeeding to sleep and co-sleeping for a long time.
So it is not really "sleep training", it is a parenting ethos. It's not likely to be The Answer for the exhausted parent who needs baby sleeping well now. It will, however, be a great way for a Mum who is happy BF to sleep and always being the baby's source of comfort for as long as is needed, to slowly start encouraging a little more independence. At a pace that suits the child, not the parent.
One of the basic methods used in the NCSS is called the Pantly Pulloff (after the author). This involves starting with a baby who is breastfed to sleep and doing a gradual process of unlatching the sleeping child. Firstly unlatching when baby is fully asleep. Then over time unlatching BF baby sooner so that they start being cuddled to sleep, rather than breastfed to sleep.
The NCSS really is not for everyone and one of the main reasons it is not for everyone is because it is not a "way to get more sleep" in any immediate way. But it gives the BF co-sleeping Mum a plan to work towards, as long as she has the patience to not rush so that it creates no distress for baby. Understanding it will take many, many months so having realistic expectations is key to having the patience to take it slowly enough.
This is no quick fix. It isn't sleep training as such.
PS - the simplest No Cry Sleep Solution in my opinion would be the dummy 