I should add that though the book was too hard for me you fully deserve our thanks for posting the link. It will be comprehensible input for some people. The need for graded readers implies that we need many levels of differing difficulty.
The reason why I wrote as I did is that there is an almost total absence of readers that cater for those like myself that find texts such as that of Anthon too hard.
I get your point about unseens being difficult if both the vocabulary and syntax are unfamiliar. I remember the feeling in my belly when that happened in the weekly unseens, was about the same as about 5 minutes after taking a big bite of a raw onion on very empty stomach - somewhere between reeching, bewilderment, introspection and the resolve to never do that again. The order in that moment of head-spinning chaos is the cases. It is surprising how little needs to be known to at least get a gist of where the meaning is going in a passage. Anthon may be aimimg his reader at students who have been trained in the accidence already, and are now moving on to texts.
Well … with that supposition about the intended readership in mind, and if you don’t mind me asking a few things:
Which authours can you sight read now?
How many thousands of words have you rote learnt?
How many sentence patterns are you confident about producing in your compositions?
Another, probably trite, question. If this graded reader approach is not working, have you tried another approach?
The greatest amount of time learning Greek I have expended is on a combination of rote learning of forms & vocabulary and reading the extant texts. My progress doing so has been zero and I have finally concluded that any further time using such a method is pointless.
I am convinced that graded readers are the only way for me to learn Greek provided they are sufficiently easy so that they could serve as comprehensible input for me. Unfortunately most graded readers such as Anthon are not any easier for me than the extant texts. Hence I no longer study Ancient Greek. I tried Anthon just in case it was an exception. It quickly became clear it wasn’t.
Images can make a difference when you almost understand a text but with your example they led me astray. The sentence is not in fact so difficult but when it stands as an isolated sentence rather than in the context of a story it is much harder.
I think that we all do (or should do) that at some point. Switching from learning to acquisition is an important step. Giving up the mental overhead of analysis and stress can be a good addition or a good new start. That is a normal part of attaining competency in a modern language too. Imagine what you woukd think if after 10 years of say Romanian, somebody still only just read texts silently to themselves, looking up every word in thge dictionary - never dreaming in Romanian, never expressing themself, never going faster than 30 words an hour!
Giving up study, or at least changing the emphasis (proportion) away from study, is a great move.
I take back what I said about your sentence. Ὁμονοούντων ἀδελφῶν συμβίωσις παντὸς τείχους ἰσχυροτέρα. is in fact exactly right for my current level of competence. The only word in the sentence that is outside the top 1000 most frequent words (using logeon as a guide) is συμβίωσις which is recognizable from symbiosis.
The fact that I initially failed is a sign of a total collapse in my self confidence in respect to Greek and the fact that I now see that it is withing my competence is a step to restoring it. Thank you for posting that example.
Skeletally, it belongs to the same sentence family as those first two that you seemed happy with. The added elements here are the genitive with a noun, the comparative degree with its genitive and the use of πᾶς in the singular.
Based on that analysis and as a means to an ends, we could compose a couple or dozen similar sentences. Choose a noun that is in someway done by people. Choose a class of people that might do the action described by the noun. Choose an action verb that plausibly describes people who do that first noun. Think of an excellent adjective that could describe that first action noun. Choose a suitable comparison to the action comparable to the people.
My first attempt is; ἐκφυγή, μετοικῶν, καταδιωκομένων, ταχύτερα and καμηλοπαρδάλεως.