As an addendum to this question, I have written a children's picturebook, and as I understand it, the process of sending off a manuscript and getting it reviewed is expected to take 3-6 months (I am based in the UK).
Is it bad form to send the manuscript to multiple publishers, or is this expected?
This is a norm that has changed. Not long ago, simultaneous submissions were frowned upon. Now they are largely expected. However, publishing tends to be an old-fashioned industry. There are still hold-outs that have different expectations, so make sure you check the submission guidelines for each publisher.
I would recommend, however, that you query first, rather than submit. This means sending a letter describing your manuscript, and waiting for it to be requested before sending it. There are several reasons for this, including that you are free to query as many publishers and/or agents as you want at any time. You are also much more likely to have an unsolicited query read than an unsolicited manuscript reviewed. You can also query in bulk, and/or tweak your query over time.
Many agents and publishers ask for the entire text of the manuscript to be included in the query for picture books, since those manuscripts tend to be very short (only a few pages of text). This still does not count as a "submission," per se, in terms of simultaneous submissions. If you are lucky enough to get multiple requests for your manuscript, each of those counts as a submission. It is appropriate at that point to ask whether simultaneous submissions are allowed, and to consider whether you do WANT to submit simultaneously or not (for instance, you might want to wait for a response from your first choice publisher before submitting to your second choice).
Most publishers are fine with simultaneous submissions and understand that it could otherwise take years for a manuscript to be accepted. What's important is to read the publisher's guidelines before submitting (they should say if they require exclusive submissions) and to be up front about it.
Because every genre has a different publishing culture, I looked up information about children's books. The Society of Children's Book Writers and Illustrators is the primary professional writer's organization for this genre. They say:
Once you have chosen the right markets for your project, you are free to send it to publishers that are accepting unsolicited manuscripts...Exclusive submission means that you will not present your project to any other publisher while one publisher has it. You can designate the length of time it will remain exclusive. But most publishers who still accept unsolicited manuscripts also allow multiple submissions, which means you are sending it to multiple publishers. You should make your submission status very clear in your cover letter...Keep copies/files of your correspondence and set up a system to track your submissions.
The way I've seen it managed is to state in the cover letter either that this is a "simultaneous submission" (the term "multiple submission" is often used but technically means sending more than one manuscript to the same publisher) or to say that you will give them X number of weeks before submitting elsewhere. I plan to use that last one when I submit my book to my dream publisher.
It is also important to send a short note to the publisher if you get an offer from a different publisher. This allows them the opportunity to move your book up in the review queue so they can decide if they'd like to make you an offer as well. Agents do this all the time.
You may submit simultaneously to multiple publishers. Publishers expect that you do.
You mustn't submit simultanously to muliple agents. And you mustn't submit to publishers before you submit to an agent.
Some publishers have a policy that they will only contact you if you are successful. Therefore, if you take the very bad advice of people here telling you only to submit to one then you will be waiting around forever for nothing if the first one rejects it. The only difference would be if their guidelines state they expect as such. But these companies will inform if it's been rejected.
Otherwise, submit to multiple then if someone accepts it you write a letter to the others stating that you retract your submission. If they have any interest in publishing your work as someone suggested, they will tell you anyway, they aren't going to go further with anything without informing you they are interested first. You still need their approval to get it published even if they do accept it because there are contracts to sign.
From what I have read elsewhere, unless they specifically mention that they accept multiple submissions, it is very bad form indeed.
The publisher has a process that takes time. If he is impressed by the mss and is working to get it published, having rivals doing the same unbeknownst to him will sour things.
Imagine you are working on a project, you go to your client and tell them it is finished and here it is. They tell you that they had it done already by X, thank you for your interest. You won’t do business with them again and will likely mention the experience to colleagues.
Multiple submissions could destroy your reputation.
One publisher at a time.
