Learn Farsi: گفته می‌شود که این کتاب راجع به یک تحلیل تاریخی است. - It is said that this book is about a historical analysis.

راجع به (râje' be) means about or regarding. Yes, you could absolutely swap it for در مورد (dar moured-e) with no change in meaning. Just remember that راجع به links to the next word using the preposition به rather than taking an ezafe (the invisible linking 'e' sound) like در مورد does.

What is the grammar behind گفته می‌شود?

This is the passive voice, literally meaning it is said. It is built using the past participle گفته (said) followed by می‌شود, which acts as the passive helper verb here. While you might often hear Iranians use the active phrase می‌گویند (they say) in casual speech, گفته می‌شود gives this sentence a more formal, objective, or written tone.

Why does یک come before the noun while تاریخی comes after?

Numbers and quantifiers like یک (a or one) always come before the noun they modify. However, descriptive adjectives like تاریخی (historical) must follow the noun. They connect via the unseen ezafe sound, making the phrase یک تحلیل تاریخی (yek tahlil-e târikhi).

How is the adjective تاریخی formed from the base word?

It is formed by taking the noun تاریخ (târikh), which means history or date, and adding the suffix ی (i) to the end. This is a very common and useful way to turn nouns into adjectives in Farsi.