The Routledge Introductory Course in Persian - Farsi shirin ast (Persian is Sweet) is a Persian language course designed for instruction at introductory level at university and adult education institutions.
This book will go on the shelf of books that made me cry, haha.
Pros: It is very difficult to find Farsi-English resources. These books are comprehensive guides to Farsi grammar, allowing a learner to organize what they are hearing and seeing in other sources.
Cons: It is insane. There is little to help an English speaker with the reading, making it even MORE difficult to learn as the learner tries to learn both the reading and the grammar simultaneously. They crammed what really should be 2-3 years of grammar and reading into one, and grouped every concept together instead of pacing it out or making concepts build on one another. For example, instead of teaching some easier verb tenses, moving on to something else, and building on everything, they put every verb tense in 3 chapters. Unless it was an easier concept, that is, which brings up another point of contention. This book uses concepts throughout, but discusses them later. For example, every verb tense is used by chapter 8, and compounded verbs are used in these discussions. But discussion on how to use compounded verbs or what they even are is not discussed until chapter 14. Prepositions are similar. Confused? Welcome to the world of poorly written Persian grammar.
The grammar is not explained well for non-native speakers. I think the primary audience here is children of Farsi-speakers who have emigrated and already have some kind of familiarity with the language. The explanations are scant and some of the English is wrong or at least a little awkward. The section on the past subjunctive is flat wrong in BOTH languages, which gives little confidence the authors know what they're proclaiming with authority. (And makes me wonder who edited this thing? Surely an English editor would notice that the section on the past subjunctive is not about the past subjunctive! Even if you go by their flawed logic, an example in the present subjunctive section belongs in the past subjunctive section, so they weren't even consistent in their error. I don't have an English degree, but I certainly noticed this rather unforgivable error for a language textbook!) Some things are easy, but on others I spent hours combing through other web sources, books, and friends scratching my head wondering wtf.
According to the introduction, this book is meant to be used in the first year (2 semesters) of Farsi study. I studied hard and am pretty good at language and grammar, but it took me about 18 months to get through it. There are concepts in here I didn't learn in 2 years (4 semesters) of Spanish, which is much more similar to English in terms of vocabulary and orthography. I think textbook writers would benefit GREATLY from consulting English speakers on concepts that are difficult to learn or require more thorough explanations. How you teach grammar to a learner of the language is very different from how you teach it to native speakers. I have an English grammar book JUST for teaching people whose first language is not English for this very reason.
I did have help through these concepts, so it's not as if I was learning them on my own. But I would expect at least some kind of practice and explanation from a textbook that I could review later. I would also expect it to be laid out in a sane way. It's not necessary to teach every single grammar concept in the first year. It's okay to spread it out over some time!
My verdict is that Farsi grammar is extremely easy if taught well, and nearly impossible if it is not. This book does not teach it well. Unfortunately, options are limited, and I don't know of anything better. Other grammar books I have seen take a similar approach. So it is useful as a guide and decent reference, but I wish I knew of something better.
Edit 8/4/2021: I found a better resource! Definitely check out https://www.laits.utexas.edu/persian_... This is free online, or you can buy a copy on Amazon. This is organized in a much better way. There are audio files and videos to accompany it, and tons of exercises to practice what you learn. It's also correct.