The Rohonc Codex is another untranslated book, lesser known than the Voynich Manuscript but equally baffling. Its origins are largely unknown. The vellum pages have never been carbon-dated, but it bears a watermark that would seem to place its origins in early 16th century Venice. It was donated to the Hungarian Academy of Sciences in 1838 by Gusztáv Batthyány, a Hungarian count, along with his entire library, but with no indication of how he'd obtained it.

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It is made up of 440 pages containing a number of crude illustrations of Biblical scenes, but also iconography possibly from pagan and Islamic traditions. The text is written right-to-left in a script containing almost 800 different characters, though many are used only rarely, indicating that it may be a syllabary or a system of logographs, rather than an alphabet.

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Source: Wikipedia