Keeping one's own spell book, more commonly known as a Book of Shadows, is a common practice in Wicca. It is not hard to see why, as it can be very helpful to keep a Book of Shadows. It is a way to keep all of your spells, rituals, and magical experiences together in one place, which makes for efficient and therefore effective spell casting.
Keeping a Book of Shadows is an opportunity to let your creative side come out, as well. Illustrate the pages, use different colored inks, and include pictures. Write the whole thing in calligraphy if you like, or use black paper with silver ink! Remember, your Book of Shadows is your personal, private habitat, so don't let anything stop you from transforming it in the way that feels best to you.
A Book of Shadows is all well and good, but where does the new witch begin learning spells and ritual? Well, there are plenty of spell books out there to purchase. I recommend reading everything you can get your grubby paws on, and then writing down the spells and rituals that work best for you in your own Book of Shadows. Also write down the spells and rituals you've modified, and the results of those modifications. This way you have everything you need close to hand and in one book, which makes it so you don't have to dig out a number of different books to gain access to the spells you need at any given time.
Some of the spell books I like are Aoumiel's Green Witchcraft, The Mysteries of Isis by DeTraci Regula, and The Druid Animal Oracle. These books are appropriate for the beginning witch as well as the witch who has been practicing for a while.
Aoumiel's Green Witchcraft focuses on nature and herb magic, and can give you some ideas for starting an herb garden. She also explains how she found her Craft Name, which is a very important part of anyone's initial "step" into the world of Magick. She is a witch that comes from a family tradition, and brings that experience to her discussions of nature magic. Her book is also written for the solitary practitioner, but a witch that practices as part of a group can still glean some useful wisdom from Amiouel's writings.
So, as you can see, there are so many different kinds of spell books that you can use to get new spells, and record the results of successful spells that you cast. There are many uses for spell books, and I'd recommend even writing one of your own based on your experiences in the craft.