So I finally struck out "Good" on my originally "Chaotic Good" wizard's character sheet and wrote in "Evil". It's funny, some of my most popular characters have been Chaotic Evil wizards, which many people consider an "unplayable" alignment for PCs.
I'm not a great believer in alignment's value, but I have played with many people who consider it tremendously important. I have therefore had to develop a "theory" of alignment.
Most people I know who really care about alignment love the version with the full nine positions, as opposed to the earlier Law vs. Chaos version. They also tend to prefer the psychological interpretation of alignment, rather than the Moorcockian cosmological interpretation.
My position therefore attempts to be comprehensible to those people and address both their desire to specifically situate any and every character in one of the nine positions and to address the psychological elements that cause them to be so situated.
Broadly speaking, I treat one's position on the good-evil axis as a matter of sentiment, conscience, and instinct.
Good people are by default deeply concerned with the well-being of others, and callousness or harm to the well-being of others is an exceptional state that requires strong reasons or experiences and is constrained to the minimal scope necessary (at least ideally). Their conscience militates for them to care as a general tendency, albeit one that can be resisted or overcome in specific situations.
Evil people tend to callousness to the well-being of others. This does not mean they are universally and completely callous, but rather that caring deeply for the well-being of others is the exceptional state of affairs for them, and is specific in the same way that callousness is the exceptional state for the good person.
Neutral people are not strongly inclined to be either particularly concerned with, or callous to, the well-being of others, and mostly default to states of mild concern or distaste unless given specific situational reasons to lean one way or the other.
In this rubric, the law-chaos axis is about whether extrinsic or intrinsic motivations predominate in one's reasoning. That is, a chaotic character is strongly driven by conscience and individual drives, while a lawful person is mainly concerned with extrinsic motivations (whether materialistic or more abstract ones like "respect" is irrelevant).
I do stretch extrinsic motivations slightly here to include extrapolations or extensions like "a right authority orders it" where the extrinsic motivation is a more just (or whatever) world built on universalisable moral principles, though I don't consider this essential to being lawful.
The focus on extrinsic motivations in lawful people tends to require their engagement with social structures or individuals who can provide these extrinsic rewards, and this engagement (even potentially antagonistic engagement if they want to do something like reform a rotten institution so it can function properly) is the basis of their lawfulness.
Neutral people don't have a strong tendency either way, and instead tend to waver between whichever of the two - extrinsic or intrinsic motivations - is stronger in a given situation.
Anyhow, all of this is codswallop since real human morality does not work this way, but I do find that this set up is more robust than most folk-theorising about alignment online, while allowing one to assign alignments to characters in games in ways that people find prima facie appropriate even when they are not aware of the rubric.
I play a lot of Chaotic Evil wizards under this rubric because I like playing characters with strong intrinsic motivations (I'm a "proactive" player) and because my characters tend to be relatively callous towards the well-being of others (they do kill monsters and harm people who resist them, after all).
On the other hand, the reason I can get away with playing Chaotic Evil characters in games is because rather than playing them as sadists with poor impulse control, I portray them as above, and often take care to make sure the other PCs are the exceptional instances of sentimental attachment.
I also try to make the inner motivations of these characters interesting and fun and then to portray them trying to actively and positively recruit others to help them realise them, while also being extremely risk-tolerant about the consequences (whether for themselves or others). This fulfils being Chaotic Evil based on the rubric laid out above, but tends to be taken extremely well by other players.
I don't have any recommendations here. I developed this rubric to form a mutually-intelligible basis for analysis with some people I play with who love alignment and who want to use it characterise the psychology of characters, and I do so successfully. I find that its development aids me in playing characters with all sorts of unexpected alignments in ways that don't diminish the other players' fun.