I only made notes on plot number 14, love - ignoring the other 19 because I was still trying to write for Mills & Boon at this point. Tobias begins with a bit of a lecture on sentimentality. I don't know if I made the connection at the time, I've not noted it, but he's making the same distinction that CS Lewis did: sentimentality relies on the reader's experience rather than creating a fresh experience for them. He's rather stern about sentimentality being a BAD THING, but as Lewis says, that might be what the reader wants. It's probably a good idea to be aware of the difference, whichever route you go down.
RB does give a good example of sentiment - a poem by Edgar Guest that goes: 'Sue's got a baby now...' we don't know anything about Sue - nothing - so we have to draw on our own associations of motherhood in order to create a picture. He says: 'an' she, is like her mother used to be:' Well, how was that? There's a whole range of mothers out there. (I am still haunted by a report I read on a child with brain damage & learning difficulties caused by 'non-accidental head injuries'. What horrors lie behind those four careful, professional words? Is that sentimentality? It's my experience and imagination filling in gaps?) Anyway, the poet goes on a few lines later to say that Sue is 'more settled like' and again you have to put your own ideas there. One person might imagine Sue previously running around with bikers, or shooting up heroin. Another reader's ideas of giddy rebellion might be Sue wearing short skirts and handing her homework in late.
As for love, Tobias says only that a love story is essentially boy meets girl BUT, and someone or something always gets in the way. All the plot hinges around the BUT. I made dutiful notes (this was 1996) but I've read better books on romances since. The most interesting point he makes is that love is not a gift, it must be earned, and that love untested is not true love.