I have always thought the same, Myrtle and Amiria. My view would always be to make the letter the best it can be and represent your work and communicate it as well as possible. But, I suppose the trouble is you read so much stuff outlining all the particular "hates" of agents that it is easy to feel crippled and scared sending off a sub as a "beginner" (whatever a beginner is.I'm certainly one.) So I have a lot of sympathy with those who feel they want to do it "right" and not take any risks at all. But, personally, I would always try and make a letter a bit interesting to read because I would feel that it represented my work. As Myrtle said, people are competing for attention - or even to get read at all. Everyone presupposes that people are actively and carefully looking for writers in the slush whereas it might be more of a case of a cursory look every now and again in the case of agents already with enough clients already but who wouldn't say no if something struck them. The letter is another opportunity to try and make a good impression or get your work across the best you can. I don't know. That would be my - very inexpert - view.

Bit late to this, but just wantewd to add in my experience. I almost always mention my wip with a sentsnce like this:
'I'm already at work on a new novel. It's called 'Mrs Somebody' and is about a woman who accidentally - and unwillingly - becomes famous.'

I had another rejection this morning (why do they always reject you on a Saturday morning?), but the agent asked me to send in the opeing chapters of the wip when it is ready. That's the third time this has happened. I'm not saying it's a massive gain, but it is a small consolation. Also, it does seem to be evidence that mentioning your next work is not a bad thing.

Well done, Saturday, that's great.

I've had a lot of rejections out of ours. It's always a shock to click on 'read mail now' and have those fateful words looming on the screen...

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or Hours, that is

Saturday - that looks like a clincher for why it IS a good idea to mention! (Well done btw on them wanting to look at the WIP and commiserations about the rejection today. Sounds like you are interesting them anyway. Maybe a matter of time...)

That's a lovely boost, Saturday, well done

Thanks, Snowy, Casey & Myrtle. Yes, it does take a bit of the sting out of the dreaded 'no thanks' letter. It's just a shame I'm losing faith in the wip/ my ability to write/ the increasingly ludicrous notion of ever cracking this publication thing.

Oh I have the t-shirt for that (admittedly now stuffed in a drawer but I'm sure I'll be wearing it again in the future)...Hope it's just a phase - you're getting positive results, it's a hard slog for most of us.