A word of warning. Don't stick too precisely to what it says in the book.

一句警告的话。不要对书上所说的抠得太死。

《柯林斯英汉双解大词典》

Let me give you a word of warning.

我来提醒你一句。

《牛津词典》

The Old Lady's word of warning.

老妇人的警告(注2)。

youdao

OK, to work. A word of warning: fasten your seat belts.

好了，开始工作，一些警告的话：,系紧你们的安全带。

麻省理工公开课 - 计算机科学及编程导论课程节选

And finally, a word of warning: the air will almost certainly be tinged a delicate shade of nicotine blue.

BBC: Prague��s historic coffeehouses

There is, however, a word of warning: the deal may require a referendum of the Swiss people to ratify it.

BBC: ?40bn held in Swiss bank accounts by UK taxpayers

One word of warning, though: these phones definitely won't fly with anyone over 10, despite what the marketing guys may tell you.

ENGADGET: Which cellphone should you get your kid?