Hi everybody!
I was looking if someone had posted this before and haven't found anything (perhaps I didn't see it - In that case I apologize), so here it is.
For those who don't know, Wikipedia has an option that allows downloading or buying a book about our favourites topics. We can make our own books from Wikipedia's articles or just read one already done. This option is new in Wikipedia in Spanish and isn't very well known here in Argentina so that's why it caught my attention, but I don't know how long it has been in Wikipedia in English (I hope I am not posting sth well known by everyone

).
So anyway, for those who don't know it: I entered Wikipedia, I searched for 'Solar System' article and I saw, almost at the end of the article, a box which said 'Book: Solar System'. I selected 'Download PDF' and got a very interesting PDF file with articles related to our System to copy to any device or e-book reader.
There're also books about 'Astronomy' and other topics related to our favourite hobby

The books can be bought, too. They print it in good format and send it to you.
Cheers, Luis.
- Again: I wish I'm not posting something obvious!