Books lost on upgrade from Drupal 5 to 6

I recently upgraded one of my site from Drupal 5 to Drupal 6 and found that the books and book pages were lost. I saw in Admin >> Content section that the content was there only the structure was lost.

Upon manually trying to recreate the books I was getting Duplicate error, so even the manual option was not working. It seems that this was a common error for many people

I did some reading and found many people have done some complex things to get around it. Let me tell you what worked for me.

Step I . I did the following steps mentioned on

1.) drop table book in D6 (if there are no diffs to your backup of D5)
2.) reimport table book from D5
3.) run update_6000 for the book module (2nd page of update, Select Version, choose 6000 in the drop-down-box for book)
4.) check your book hirarchy

Step II
: I was geting some duplicates in book navigation , so I deleted the duplicated entry for top level page from menu_links table. The entries to be deleted are the ones which has "has_children" = 0 and not 1. Remember this was only for my Top level book page.

And everything else worked like charm.

This is a bug from the core team and I sincerely hope its fixed in D7 upgrade