When setting a section with a lot of two line paragraphs I personally try to have the page breaks between paragraphs. This means ending pages a line short frequently. Sometimes it is possible to give or take a line if there is a picture or figure on a page to adjust the layout. I try extremely hard to have the same numbers of lines on each spread. I find this very important. If a page lack a line, both pages on that spread should lack a line.
As long as I'm consequent and have good reasons, I feel I can stand by my choices and defend them if anybody asks. None of my clients/editors have ever mentioned anything about it, and I honestly do not think the public in general notice.
Also I find it faster to handle incoming corrections after proof reading if I do the layout in this way, an advantage when deadlines are tight.
I'm sure others have far more sophisticated ways and other rules they follow.
Best of luck with the book.

Thanks for the reply. I agree completely, yet there are still times when the text seems to fight back. In the book I'm working on now, there are SO MANY 2-line graphs that the "line short" solution on one page creates problems further along, and I find myself going round in circles. As it happens in this book, most times the last line of the paragraph is a half line in length, so I can't adjust the tracking to bring a line up or down. Pages that are 2 lines short look awful. Should I go into real estate? :)

When I find myself going in circles like you describe, I have on occasions removed a line above a nearby header to see what looks less disturbing to the layout. Most often the missing line above the header looks worse. I tell myself for comfort that a lot of short paragraphs on a spread will camouflage the missing lines at the bottom of the pages.
There is another solution that is a bit more on the dark side, but on the bright side gives you perfect text distribution. It involves reading the text and edit it, without changing the meaning, until the layout is perfect. Not recommended as the outcome could be much like in real estate ...