I am partial to it, of course, but I think it is a very useful introduction to ancient Greek in general, no matter what you plan to read.
If you wish to read Aristotle, you may consider these Greek commentaries:
For me, the Greek Ollendorff, with its methodical and extremely simple progression, was a perfect vehicle for recording and then listening, as an autodidact’s way of complementing grammar study with the development of some natural feeling for the language. I wouldn’t recommend the Ollendorff as one’s sole or first general introduction to (yes, Attic) Greek - there’s too many excellent and much more contemporary resources for that.
As for a “gentle introduction toward reading Aristotle [in Greek],” there’s no such thing. In addition to the complexity of its subject matter, the style of Aristotle’s works is generally that of classroom notes, highly abbreviated and full of shortcuts. I’m no expert, but decades ago as a classics PhD student I took a graduate seminar on Aristotle that was focused on his compositional style, and I remember it took considerable effort to begin getting comfortable with it.
If your goal is to read Aristotle in Greek with some facility, I suggest you need several years of preparation, learning (Attic) Greek in any of the standard ways and then reading other more “connected” prose first (Xenophon, the “early” dialogs of Plato, some Thucydides, maybe some of the Attic orators, …).
Randy Gibbons
It would be wonderful because we have two wonderful audio companions which are freely available:
https://archive.org/details/GreekOllendorff96
https://www.dropbox.com/sh/v99kn4b0jht4vcy/dKRQeLWj3Y
But Randy is correct that you would still have lots of additional work you would need to do before you could comfortably read Aristotle. But it’s a start, and you could listen to the audios while commuting to work.
I would have expected “What is this?” for “Τί ἐστι τοῦτο;”
And rightly so! What a silly error. It shall be fixed by close of business today. 
Διώθωκα τὸ σφάλμα μου. 
The missing Exercise 107
The downloadable version of Ollendorff has two pages missing. Partly as an exercise I decided to type up the Greek exercise and am posting it in the hope that others may find it useful. (I have rechecked it for typos though I suspect that I may have missed a few. 
)
πόσος χρόνος; Τοσοῦτος χρόνος. ἐν τοσούτῳ χρόνῳ. ὑμῖν οὐκ ἔστι τοσοῦτος χρόνος ὅσος ἡμῖν. πόσον οἶνον ἔχετε; οὐ τοσοῦτον ἔχομεν οἶνον οἱ φίλοι ἡμῶν. πόσοι νεανίαι εἰσὶν ἐν τῷ κήπῳ; οὐ τοσοῦτοι ὅσους ὁρῶ ἐπὶ τοῦ λόφου. οὐκ ἐκεῖ τοσοῦτοι νεανίαι εἰσιν, ὅσα ῥόδα. τὰ ἐν τῷ κήπῳ ῥόδα οὐ τοσαῦτά ἐστιν ὅσα τὰ ἐν τοῖς ἀγροῖς. ὁ παῖς οὐκ ἔχει τοσαύτας ἀργυρᾶς σφαίρας ὅσας ἐγώ. οὐ τοσούτους λαγὼς λαμβάνει ὅσους σκιούρους. ποῖον οἶνος ἔχετε; οὐ τοιοῦτον οἶνον ἔχομεν οἶον ὑμεῖς. ὁ ἐργάτης οὐ τοιοῦτον οἶνον πίνει οἶον πλούσιος ἔμπορος. πηλίκα ἐστὶ ταῦτα τὰ κακά; τὰ ἐμὰ κακὰ οὐ τηλικαῦτα ἐστιν ἡλίκα τὰ σά. πηλίκος ἐστὶν ὁ νεανίας; οὐ τηλικοῦτος ἐστιν ἡλίκος ὁ ἀδελφάς μου. οὐχ ὁρῶ τοσαύτην σοφίαν ἐν τῷ διδασκάλῳ τούτῳ ὅσην ἐν τῷ μαθητῇ. αὕτη ἡ σοφία.
Daivid, you can get it from the Google Books version.
True but it is not downloadable. (If there is a way to download stuff from Google Books please let me know.) I find using Google Books online awkward and the benefit of those who are like me, I posted a version that can be cut and pasted.
Just click on the cog on the top right and select “Download PDF”
Having not seen a way to do that first time I stopped looking. You have my undying grattitude for that tip.
On the page with the key to that exercise you warn people that the two pages are missing from the Internet Archive. It might be useful to mention that the Google version is complete on that post.
Hi, Davidhan,
Lessons 32 and 33 are in the same post. Probably that’s why you missed it. You may want to download the free pdf or buy the printed edition on Lulu.
Possibly one like got dropped out of the key:
On page 158 between - Ὁ πατὴρ πέμψει πρὸς τὸν ἰατρὸν διὰ
τοῦ υἱοῦ. and - Οὐ διὰ τοῦ τοῦ ἐμπόρου υἱοῦ, ἀλλὰ τοῦ διδασκάλου. there is the phrase Not through his own son but mine.
Something like οὐ διὰ ἑαυτοῦ υἱοῦ ἀλλὰ διὰ τοῦ ἐμοῦ perhaps?
EDIT
Also shouldn’t Εὑρήσω τὰν χλαῖνάν μου ἢ πρὸ τῆς θύρας, ἢ ἐπὶ τῆς τραπέζης, ἢ ἐν τῷ χρυσῷ κανῷ. have τῇ χρυσῇ χηλῷ at the end?
Once again thanks for doing the key. Even though I am doing stuff that should be revision the key allows me to spot places where I hadn’t quite got it.
Many thanks for spotting my mistakes. I corrected them here and also in the lulu version.
But in the exercise it has for the last sentence:
The shepherd remains many months in the field.
And thanks again for providing the key
Thank you for spotting it! It’s fixed now.
Hi Bedwere - the pdf link on archive.org is now dead - it says ‘there is a problem with the content’
I contacted archive.org to know what is going on. In the mean time, you can find it here.
I’ll remove this once the problem is fixed.
The good folks at archive.org have fixed the problem. Now the key is live again:
https://archive.org/details/Bedwere_Key
This project looks to be finished. Thanks for your hard work preparing these very useful materials.