In this site you can find a lot of books from a lot of different themes.
About Brasil I recomend:
História concisa do Brasil - Boris Fausto;
História do Brasil - Boris Fausto (this one is quite big in comparison with the first indicated, hence more detailed);
http://editora.fgv.br/colecao-fgv-de-bolso - Livros de bolso(in this site they sell short books in different topics, I enjoy reading because it’s easy and worth; they have many of them);
http://funag.gov.br/loja/index.php?route=product/category&path=70 - some goods free books;
1964: História do regime militar brasileiro - Marcos Napolitano;
Raízes do Brasil - Sérgio Buarque de Holanda;
Da Monarquia à República - momentos decisivos - Emilia Viotti.
Of the world:
A Era das Revoluções
Era do Capital
A Era dos Impérios
Era dos Extremos - o breve século XX - All from Eric Hobsbawm, he’s a marxist but still being worth. You can find the equivalent one in english;
História do mundo comtemporâneo - Paulo Vincentini
Pós-guerra - Tony Judt
There’s more but I’m lazy and I doubt you will read all of these.