convert a pdf book in indesign editable

If you can't get the original files, and you have permission to make changes, and the PDF is high quality, place the PDF into a new InDesign file using the place multipage PDF script (Window> Utilities> Scripts> Application> Samples), make type changes by setting new copy in InDesign using the same font as the original PDF, as determined by using the Output Preview tool in Acrobat (Preview: Object inspector).* Delete the original unwanted copy in Acrobat (Tools> Edit PDF), export to a new PDF/X-4.

This will work unless there are major revisions spanning multiple pages, in which case purchasing software to convert the PDF to an InDesign file (as a starting point) might make sense. Don't forget bleed.

*To match the original type style, set the exact same copy in a different color, adjust the spacing until you get a perfect match, save as a style, then make your changes.

Use the appropriate commenting tools:

I think too many assumptions are being made about the original files...

Does the designer work for your company? 

1] If yes, you should be able to get a copy of the files unless the designer is trying for job security.

          A] You may have to get your dept. boss involved.

2] If no, you need to check what the original work agreement was with the designer/agency.

          A] If "work for hire", your company owns the files

          B] If there was none or file ownership wasn't mentioned, then the designer owns the files. 

                   a] Is the designer going to continue to work with your company?

                                   i] If yes, then it is to their benefit to turn over the files even if it means some minor lost work.

                                   ii] If no, the designer has no incentive to turn over the files and you should offer to pay for them.

If you can't get the files at all...

1] You can get a third-party utility to convert the PDFs to InDesign files, but you may need to spend a lot of time cleaning the files up.

          A] Check out Markzware.com and Recosoft.com for their plugins.

2] In Acrobat Pro, convert the content from the PDF and rebuild the file.

          A] You can export the text to Word.

          B] You can export all the images as separate files

(The forum software really mangled my original bullet list...)

It's industry standard to send press-ready PDFs only. You paid for the finished work, not the working files. 

If you are still in touch with the designer, you ask see what they would charge to make the changes, or how much it would cost to purchase the working files from them.

you can't..... you need the "packaged indesign files" from the designer. ask for that. It should be a folder with the indesign file, a .idml file, a folder called fonts with all of the fonts used in the layout, and a folder called links with all of the linked art.

If I had to guess, the person that created the pdf and sent it to you, didn't want you editing the indesign file. Have you requested the indesign file? Sometimes designers don't turn over native files because they'd like to have your repeat business, as in make any changes for you that you need. 

Get the original InDesign. Anything else is going to cost you a world of work.