The sort of "beginner" that Mercer seems to have had in mind is someone who has already studied several languages and is familiar with grammatical terminology. Probably most of his students had already taken Latin, Greek, and a modern language before they ever sat down to study Egyptian.
If you do not know what a 3rd person plural perfect active indicative verb is, you are likely to have trouble with this book. It presupposes quite a bit of grammatical knowledge. I consider this a problem with the text.
On the other hand, Mercer also states: "The author's object has been to make this book as brief and concise as possible." In this he has succeeded admirably. The book is concise. If you do have the sort of grammatical knowledge that he assumes you have, then you will probably appreciate the compact nature of his text.
Reading this book should take time. Mercer packs so much information into each sentence that you need to read slowly and carefully in order to catch everything, especially when the sentences are broken up by long sections of glyphs. Reading each section multiple times is probably a good idea if you want to learn the topic well.
As Mercer states, each chapter is supplied ". . . with copious exercises." You should do these exercises. Get paper and a pencil (so you can erase mistakes), then copy out the glyphs, write the transliteration beneath them, and then the English translation beneath that. It takes a long time to properly copy out glyphs. The longer it takes, the better you'll learn the material, since you'll be thinking about them for so long.
I should mention that I have altered the exercises slightly. In the original, the exercises are rows of glyphs separated by commas. I have taken the liberty of putting each sentence on its own line, so that it is easier to tell where one sentence ends and the next begins. I've also done this for the vocabulary.
Speaking of vocabulary, I don't know when I'll get around to putting up the Sign List that Mercer mentions. It's just that -- a long list of signs, organized by what the symbols resemble. All the human-shapes are put together, and all the bird-shapes, and so on. Beyond that, there is very little in the way of organization. Looking up Egyptian words is pretty near impossible. Basically, you have to scan down the list until you find the symbol you're looking for. Furthermore, there is no correlation between the Glossary (where he defines each Egyptian word) and the Sign List. Looking words up in this book is a serious pain. I recommend getting an Egyptian-English dictionary from a library, if you can.
Remember that vocabulary is sometimes found in the text, rather than in a list. This will help you when you need to find words.
It will be a while before I put up the Chrestomathy, which consists of long Egyptian texts in hieroglyphs for reading-exercises. They are many and long, and will take up quite a bit of space, not to mention effort in cleaning up and compressing scans. So it will be a while. As I've said before, this is a long-term project.
Now you're ready to start reading; go to the Table of Contents.