here's a little tip

Never write a textbook.

Unless, maybe, you're tenured and you REALLY feel the need to write one.

Otherwise, doing so will ruin you.

Okay, maybe not ruin you. Not if you work for an institution that values textbook-writing. And not if you are rewarded for writing one. And not if you really, really want to write one.

Otherwise, it will ruin you. If you find yourself in a position similar to my own, it will ruin you.

Unless, of course, you have an official guarantee from the Provost's Office that you will be granted tenure despite all the time you spent working on a textbook instead of doing other things like grant-grubbing.

Even if your textbook is the "most highly and consistantly praised" your editor has ever seen in his many years with Major Academic Publishing House, committing to and writing a textbook before you are tenured will ruin you.

Even if--or, especially if--you are co-writing said textbook with two of your colleagues.

Newly hired academic dearies, do not write a textbook. Unless you meet the unless-es of all of the above.