Here's a sentence on the back cover of an edition of Roughing It in the Bush (Virago, 1986):
Her absorbing book, reissued in its full version and with an introduction by Margaret Atwood, whose first volume of poetry, The Journals of Susanna Moodie, is testimony to the enduring spirit of a remarkable woman, has been out of print in Britain since 1852.What a wonderful example of horrible punctuation. The author has created a 44-word sentence chopped up by five commas. Margaret Atwood would be horrified.
I thought perhaps the back cover sentence was an homage to Susanna Moodie's writing style, but Moodie's sentences are as crisp and clear as an autumn afternoon. Let me qualify that somewhat: an autumn afternoon in 1832. But still -
I suggest dividing the offending sentence into at least two sentences:
1. Her [Moodie's] absorbing book has been out of print in Britain since 1852.
2. The new version includes an introduction by Margaret Atwood whose first volume of poetry, The Journals of Susanna Moodie, is testimony to the enduring spirit of a remarkable woman.
Count the words in your sentences or count your commas. Either action will help you if you want to write better (dammit).