Didn't realise they were 5 weeks adjusted age, that is still the age of chaos. If you feel a routine would help you in the next few months then go for it.
I didn't have any problems dropping the night feed. Just stopped it one night, waited with baited breath and they slept fine.
I found the books useful. Like most people I didn't follow them to the letter, but just found it useful to have some guidance - a bit like mumsnet really! I had never had babies before, knew no one with babies (was the first one of my friends to have children), had not grown up around babies or ever handled one.
I had not got an inkling how often they should be fed/why they were crying - the whole "follow your instinct" thing just didn't happen for me, even though I loved them hugely and was delighted that they had arrived. Trying to "naturally" respond to two babies needs at once was beyond me.
I posted a similar post on a website when my girls were about 8 weeks and some people advised me to ignore the books and ignore routines.
But for me a book was like having a friendly aunt, that could just give me bits of advice and I could choose which bits I took. And having both babies sleep at the same time every day and wake up refreshed and happy was a godsend.
I never had to leave them to cry to settle into the routine, instead I just gently persevered with putting them down at the same time each day for their naps. And they are now two lovely, happy, lively little girls