Brought into line, book parts rather like Peter or Roger? (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

B (book) + BIT (parts), all contained by (brought into) RAY (line). I’m probably missing something / making something up here, and probably not for the first time today. I am missing quite a lot: B (book) contained by (parts) A BIT (rather), all brought into RY (railway, line).