The New Testament was orginally written in Ancient Greek (or, more specifically, Koine Greek) and is written in a mostly rather easy to understand manner; this is due to the fact that it written using simpler grammar and repeats things frequently. I therefore find it to be a great text to read as an intermediate student of the language — especially if you are Christian or interested in Christianity.
Ἐν ἀρχῇ ἦν ὁ λόγος, καὶ ὁ λόγος ἦν πρὸς τὸν θεόν, καὶ θεὸς ἦν ὁ λόγος. These are the opening words of the Gospel of John or, as it is known in the original Greek, Κατὰ Ἰωάννην (Ευαγγέλιον). And whilst I am aware that it is not literally referring to a
word per se, I find it to be a fitting quote to display here. As briefly mentioned above, the New Testament's original language is Ancient Greek, and although it hadn't actually been written by a native speaker of the language, I would still consider it an invaluable resource for learning the language.
This is mostly due to the aforesaid fact that the New Testament — and the entire Bible, for that matter — are written in a somewhat simple-to-grasp manner with lots of repetitions. I am by no means saying that one will be able to read the Bible fully without any issues whatsoever after only a minor amount of time spent stuying, but it is, I would argue, amongst the easier texts that can be read. This is undoubtedly because of the type of Greek it has been written in — namely Koine — which utilises a much simplified grammar when compared to Attic.
Though I must give credit where credit is due and proclaim that the idea of getting the New Testament in Greek was not my own idea; rather, I had written a small
letter to my English teacher — who knows Ancient Greek — who replied to my question regarding reading resources by telling me to get a Bible. He had initially recommended that I get a bilingual version — which I still might — but I decided to, instead, buy a regular, mono-lingual version. This is mostly due to my not wanting to spend over €50 for a new copy of the bilingual version and my not being able to find any second-hand editions. I was, however, able to find this pocket edition containing only the Greek text for roughly €10 on eBay.
Though I must admit that this pocket edition of the Novum Testamtum Graece is not my favourite way of reading the Greek New Testament. It is a lovely and small book that you can take anywhere, but lacks in practicality for a lower intermediate student of the language; there is no dictionary, no notes. Instead, the pages are filled with cryptic symbols representing textual differences, something you most likely do not need unless you are a theology student.
It is, however, a handy book to have if you want to reinforce what you have read previously; a part of the book you know well enough to comprehend without a dictionary. Nevertheless, for actually reading new parts of the New Testament that I haven't read before, I generally prefer using The Greek New Testament. A Reader's Edition and I recommend you take a look at that page if you want further information regarding that book.