I published a book last year with black and white photographs in it as jpg files inserted into the text. The document looked fine as a pdf file and the electronic proof pdf file looked fine too but the printed pictures were way too dark. I redid the book after lightening the pictures and the revised pictures look ok but I guessed about the amount to lighten them.

Since then, based on a suggestion, I bought a Colormunki Smile monitor calbrator and calibrated my monitor. But now what? The material which came with the Colormunki doesn't cover anything other than calibrating the monitor. Does anyone have any experience with Colormunki or other monitor calibrators?

The purpose of that equipment is to calibrate your monitor to certain standards so the image quality on your screen accurately represents what will print or others will see on their screens. Suggest running another test using an image that looks good on your calibrated monitor. However, since the previous electronic proof looked good, I suspect the problem is not on your end... (Does the previous electronic proof look good on your now calibrated monitor?)

(Disclaimer: I'm into photography, but have not used that equipment or published anything. Just trying to explain what it does.)