1) The core Drupal Translation module works good enough for me for most content types with the notable case of books.

In the case of books, all pages are diplayed whatever language is selected.

2) I am trying the i18n module, but the situation, though different, is not better: the correct pages are now displayed when selecting the "source" language, but the block books itself totally disappear when selecting another language.

Comment: I did not found any useful documentation nor forum posts about how to properly manage multilinguang books. May be I don' use it correctly.
For example, should translated pages be outlined similarly to the original page, or not outlined at all, or part of a separate "ghost book" with some identification rules to link them???
Is the rule the same if we use or not the i18n module?

Thanks for help