Writing a book/manual: software and help?

You might get some better answers if you ask this question in one of the science categories.

Is this book something you're planning to submit to a publisher, or is it a dissertation or thesis for a degree? A publisher will probably have their own ideas about how the book should be laid out, so you don't have to worry about that, as long as all the content is there, and you can explain how everything fits together.

Many years ago, I was briefly responsible for some of the company's technical documentation, and we used Adobe FrameMaker for it. I found it a joy to use in comparison to MS Word. It's still around, but I don't know how it compares to any other products that are available now. It's also quite expensive.

Lately, most people who I've seen talking about writing scientific papers seem to be using LaTeX, which is open source, therefore free to download and use. (You have to spell it like that when you Google for information about it, otherwise you get pages about something else entirely.) I've never used it, but I'm told it's very good for equations and graphs. The drawback is that it's not a graphical program - instead you have to write instructions describing what you want the output to look like (a bit like HTML, if you've ever written that). There are apparently graphical front ends for it, but I don't know how good they are. See here for an introduction to it - https://en.wikipedia.org/wiki/LaTeX

Hi, I have been in the midst of writing a "manual" if you will about my field of study, which happens to be engineering.

Anyway, I have been writing this in Microsoft word. And I m afraid that eventually I ll have to go back and change so much stuff to make it look professional.

So my question is, what software makes writing a manual easy? Like adding distinctive headings, figure numbers, etc.

I want my work to look 100% legitimate. And it MUST be printable. Keep in mind this is a complex writing, with many figures (graphs) and a complex hierarchy of topics. I must establish an order in my topics so the reader understands.