The process you describe should work. I've done it much the same way on several books.
I first convert my color images to black and white since the cost of printing color is prohibitive. Then I increase the contrast as much as I can without erasing the distinction between different areas. That done, I increase the intensity quite a bit since the printed version of the image is duller than what you see onscreen. Finally I print up a proof copy to see how well the results were. I have to do this two or three times for a book to get what I want.
I use an inexpensive consumer version of Photoshop (PS Elements) which has most of the features of full Photoshop to do this. The exact path is
Enhance -> Convert to Black and White. The popup screen gives you several choices of how to do this. I choose Scenic Landscapes first, then several others. After finding the best one for my images, I then tweak the result a bit.
You can get free software such as GIMP to process your images, but the how-to information for it and other free SW is not too well written and organized. You can save yourself an enormous amount of time and frustration by spending $70 on PsE and $30 on a good user guide. The following book I recommend has well over a hundred illustrated step-by-step guides to do everything you might want to do to your images.
You hate to spend money when self-pubbing a book? Want to get everything for free? It doesn't work that way. You will always spend SOMETHING, and time is the thing you have least of when trying to create a quality product which will bring people to buy your books and convince others to do the same.
http://www.amazon.com/dp/B014GP8XGM/?tag=absowrit-20
http://www.amazon.com/Photoshop-Elements-Digital-Photographers-Voices/dp/0134290895/