I want to force Adobe Indesign cs5 to begin any chapter of a book file on any page, odd or even, how can I do this? In other words, not leaving any blank page. Thank you, Ed
It depends on how you added those page breaks in the first place.
Manually with "Insert Odd Page Break" and/or "Insert Even Page Break": add a regular "Page Break" (without 'odd' or 'even') immediately after the current page break, then delete the previous break. (Do it in this order so you cannot accidentally paste the previous and next paragraphs together, which will mess up your paragraph styles.)
See the Online Help: Add column, frame, and page breaks.
With a paragraph style: change the style's Keep Options, "Start Paragraph" from "On Next Odd Page" or "On Next Even Page" to plain "On Next Page".
See the Online Help: Control paragraph breaks using Keep Options
Manually through Keep Options: go manually through each of your chapters and adjust the Keep Options of the first paragraph.
While you are doing that, ponder upon the positive points of using styles. For that, see the Online Help: Paragraph and character styles.
With multiple documents in a Book: in the flyout menu of the Book Panel, go to "Book Page Numbering Options". Instead of "Continue on next odd page" or "Continue on next even page", choose "Continue from previous document". Make sure the checkbox to update existing page numbering is checked. If you previously added blank pages this way, you need to remove them manually after changing this setting -- InDesign does not automatically "remember" it added them earlier on.
See the Online Help: Number pages, chapters, and paragraphs in a book , subsection "Start numbering on an odd or even page".