Is out there a free software ?

Open Office has a powerful word processor that will do a fair job of book writing. It is a huge download but is also on the cover discs of many popular computing magazines. A very powerful suite of programs and totally free.

As already mentioned, Open Office is the best freebie around. However, it looks like you want some kind of book-publishing tool. You don't actually need one. Most of the online self-publishing sites (lulu, etc.) will accept PDF files, so you can just create them in Word (or the OO equivalent), and convert them with a doc-to-PDF converter. Some just want raw text which is then auto-formatted at their end. If you want the A5 book layout, it's easy enough to do by just redefining page size and layout - either as A5 with a gutter margin (more professional) or as A4 landscape with two columns (easier). I've never seen a free app that's specifically designed for book layout publishing, to be honest, since most modern word processors are publishing tools as well.

I am sorry, I do not know of any software like those you mentioned. But you could always write the book in WORD then convert to PDF through Acrobat. PDF is widely known and accepted, you see. Have a nice day!