The English word forte (the one that means "strong point") comes from French. But the original French word is not forte. The French word is, in fact, fort, which is pronounced without the "t" at the end. And yet when this word entered English, an orphan letter "e", looking for a new home after its parents were brutally murdered by Germans, was added to the end of the word. And so the English word became forte. And with this new spelling came a new pronunciation. Some half-clever English speakers showed up who knew enough about French pronunciation to realize that if there's an "e" at the end, that we're supposed to pronounce the "t".
And so in English, we started pronouncing the word forte the same as fort, as in a defensive construction that can be made of concrete, wood, or pillows. English forte and French fort have identical meanings, but the English pronunciation had already begun to wander away from its origins.
The story doesn't end there. We also have another English word forte, this one a musical term borrowed from Italian. This other word, with a completely different meaning and etymology, is pronounced with two syllables. But in one of those wonderful linguistic coincidences, it is spelled identically to the new English spelling of the French word fort. And in the resulting confusion, the ruggedly handsome Italian pronunciation wooed English speakers away from the flaccid faux-French pronunciation, which just couldn't compete in the charm department, perhaps because it wasn't genuine in the first place.
So now we have two words that are spelled the same and (mostly) pronounced the same, but with two different meanings that are the result of their different etymologies.
Some prescriptivists still like to insist on using the faux-French pronunciation for the word that means "strong point", but these people are high on fake cheese and wine and can safely be ignored. Dictionaries still list both pronunciations, but the "fort" pronunciation of forte is pulling a Terry Schiavo. The only reason it hasn't been unplugged yet is interference from people who don't know when to let go.
In my first trip to grad school, surrounded by language, I picked up an interest in English grammar and usage. I never had any formal linguistics training, but friends of mine were linguists and I read their books and starting reading Language Log. This didn't make me an expert, but it did mean I knew more about grammar and usage than 99.9% of other English speakers.
That's close enough to being an expert for me.
The best usage guide available on the market is the Merriam-Webster Dictionary of English Usage. But it's old and not particularly well organized. Garner's Modern American Usage is newer and more stylishly presented, but also more stodgy. The advice in his miniature essays is almost uniformly great, and his individual entries would be much improved if he took his own advice more seriously.
I'm not insane enough to have an actual plan to write a usage guide myself. But if I did, it would be called The Devil's Dictionary of English Usage, and this might be one of the entries.