"Genki 1" is a product worth trying out. My astonishment over how much Japanese writing was in this book when I first looked at the introductory page went by fast as I understood that the introduction was in both Japanese and in English. So no worries there, this book is strictly for beginners.
When I first tried to learn Japanese there were many uncertainties, I didn't know how to go about it and i was fumbling in the dark at first, switching from teaching myself Hiragana to attempting to tackle the grammar. A friend of mine showed me a book called "Japanese for Dummies", it's a fairly good book, but it seemed to be more of a phrasebook-approach and there were no Japanese writing. The issue was that I got a very funfactual approach and though I would have learned to pronunce some simple sentences I would never learn how to read or write it.
I did know Hiragana before I bought this book, I could read and understand it fairly well through practice and games on the internet. That's an advantage, when you open a new book full of learning material it's not always motivating that you have to learn a bunch of stuff before you can begin reading the actual book, so knowing Hiragana and some Katakana before you get this book is very important. In that case I would reccomend the internet, there are alot of alphabets and explanations there for the two writing systems. There are also a variety of games that you can find, this will force you to learn the actual letters, not only the order of them if you try to learn them by a list.
So when I bought "Genki 1" I did it in a hope to get into Japanese in the fall semester *fingers crossed* as it is curriculum here and I could go about it at once beacuse I already knew alot of Hiragana from before. The book has the typical romanized Japanese spelling as a supplement, believe me, it should only be a supplement. I use a piece of paper when I read so that I can use the romanized form only as a corrector when I read the Hiragana, only after opening the book a dozen times I already have tons of Hiragana reading esxperience. The advantage of this approach is that you get motivated by the interesting signs that make up Japanese writing system. Slowly the book will move away from romanized letters and soon you will be on your own having to depend on the Kana reading skill alone. By chapter 5 there will be some Kanji as well and slowly the book will move to becoming the typical Japanese symbiosis of Hiragana, Katakana and Kanji. All along the way you have translations and explanations in English of course. When the Kanji come in the Hiragana will exchange romanization as a reading supplement so you do not have to know the Kanji-symbol instantly.
Do not worry though, to supplement this book I would recommend "Remembering the Kanji" by james Heisig. He has also written a book called "Remembering the Kana", this book explains the Hiragana and Katakana writing systems in a new way by using association memory instead of the usual memorization approach of remembering and forgetting on and on again until you finally learn it. For example the syllable "ki" looks a bit like a key and by use of associated memory you will remember it easily because you connect the meaning to a typical imigary and this image will pop up every time you try to remember this syllable. I did not use this approach by learning Hiragana so I'm not shure how it works, look into it though as it may save you some time. "Remembering the Kanji" though I tried and it supplements "Genki 1". It uses that approach and for now it has worked very well. Before I used this method I only knew about 7-9 Kanji, after one hour I knew 30.
Study the book often, it does not give you any pronunciations, the Japanese meaning or the whole variety of meanings, it only gives a meaning (I will only show as I, not watashi, one will only show as one, not ichi) and maybe a key word meaning. But it explains very well how to put the Kanji puzzle together in an effective way, later on you will be able to apply these meanings and also be able to recognize the Kanji in "Genki 1". Be aware though, Heisig does not use the ordinary school order, he mixes the order up to make it advantegous to learn it HIS WAY, not using the order in "Genki 1" but I think it will be useful nonetheless.
Genki as very good bok, it is easy to understand and motivating and gives you an interesting view of the language and as you are able to read more and more confidently you get the rewarding feeling that strictly romanized learning material can't. It gives you a whole new feeling of mastery and skill in handling the written language, you will not turn the page without learning anything you will be motivated to learn those simple introductory words and sentences because at the same time you will learn a new and interesting way to read a language.