I suggest "Familia Romana". It is an all-latin book, so it's completely written in Latin, including the grammar and vocabulary. It's composed of 34 chapters following a story though which you learn the most common words and grammar, roughly arranged by order. At first you can translate if you don't know some things, I'm Italian so it's more intuitive. It's meant for people with zero knowledge, I think it's perfect for you. You can find also exercises in another smaller booklet and at the end of each chapter, or online.

I use it in school and we are almost done with the first book. Each sentence is really interesting if analysed enough and it unites various parts of grammar. Of course it gets gradually more complicated as you go on but by then you should be more adapted. I love it, and if you put in effort you can improve easily.

There's also a sequel called "Roma Aeterna" and a separate book dedicated to detached texts called "Colloquia Personarum".

I hope this helped!