I would steer totally clear of any book that tells you 'This is THE way to do it'. There are as many ways of parenting as there are children. I might not have years of parenting experience and have looked after hundreds of babies, but I have four and a half years worth and have looked after 3 children who are all entirely different. If I had tried to get dd2, now 8 months, to do the GF thing, it would have worked like a dream and I would have put it all down to Gina. As it was I tried it with dd1, who had a totally different temperament, needs and personality, and it was an unmitigated disaster, to the extent that it exacerbated my PND to the extent that I was sectioned into a mother and baby unit. My psychiatrist was adamant that trying to make my baby do what it would not do (in her case, sleep 2 hours after waking up, because all babies are tired then) was the most important factor in tipping me over the edge.
I don't blame Gina for putting me in a psychiatric unit (any more!!) but if she had not said that this was THE way then I would not have fallen to bits when dd1 would not do it.
I might not be a nanny with years of experience but I know my children intimately, their personalities, their needs, wants, likes and dislikes, what soothes them, what does not (never try cuddling my ds when he is angry, it drives him wild, but dd1 comes to you for cuddles when something has angered her). We don't expect adults to run like clockwork so why children?
My children have a routine for waking, eating, bedtime, sleeping, which is one we worked out over the years as they have grown and developed,and they have fitted into it together. What I wanted was flexible children who I could take anywhere, and by allowing them to develop their own routines that is what I have.
I could write a book - 'How To Look After Susanmt's Kids' - but I would never presume to say that cos I do it with mine you should do it with yours. So I would stay away from any book that insists it knows how to bring up ALL children according to any kind of formula (I mention GF only because it is the one I have experience of).
Someone said reference books, for health etc, and I would agree with that (we don't, but only cos dh is a doc so I can ask him). Apart from that there are no parenting books on my shelves - that's what Mumsnet is for.
I'm sorry if I offend/upset any GF followers - I know for some of you she has been a true sanity saviour. But it must also be recognised that her way robbed me of mine for a while.