I am a writer who has just started- It's part-time as of yet. I have begun several books to no avail. Sadly, the book I take as my greatest success is a Cristian fiction, not because I am ashamed, but because it is unfinished and I was aiming for Fantasy. Has anyone got any tips on how to get farther, with more interesting topics and to be able to take control of where my book steers itself?

You are in control of everything you write.

If it is not heading in the direction you want then rewrite it. Sometimes it is best to write up a story time line. When, Where and Why is something you need to constantly ask in each scene. Everything you write needs to matter to the rest of the story. Dont just shoot the breeze.  Write up character profiles, know your characters likes and dislikes. Do they have milk in their coffee? Sometimes it is easier to just sit down and write from start to finish BUT you have to go back and edit and change. It is a great way to get a draft story idea out and see if it works. (I am doing a 50,000 word challenge at the moment, doing two stories, one is working the other is a struggle)

See if there are any writing groups in your area, writing with others is great and a nice way to learn from others.

Sit down and write every day that is the only way to get a book written, it will soon become habit and easier.

Not sure what you mean by interesting topics though.

One thing I know in fantasy is, if ya dont like something then change it to suit yourself.. IF you use magic, make some rules and then dont break them nothing ruins a story more then incosistancy.

I would say don't take control at all.

The way my writing works best (and the trick is no two writers agree on the best methods) is to usually come up with one little idea or emotion, such as a man in a sci-fi setting facing the facts that his first true love intrest is dead and the enemy is converging on their position bent on eliminating them. That moment when the pain just slips away and he calmly proceeds to do a kamikazi style attack that changes the course of history for the war.

That starts all from the emotional moment where you realise that it's all gone and that in some ways you have no more responsability to reality and you have but a short time left. What mark do you leave behind, how do you justify your actions to yourself (as nobody else is lible to remember or know about it).

The rest of the story is just filling you in to the subtleties of the setting and characters. It's a war? when did it start, and who the enemy? Why are they the enemy? Who are the allied forces? Why, and how long have they been there? He lost his love intrest? Did she know how he felt before she died? What is the story of their relationship? Who is effected how by the events of the war, and the pivotal moment of the story?

Now you have the emotion of the story, and the motion of the story, you just need the words that carry it. So write. Let the story write itself. You should find that the information you have learned from years of interacting with people will tell you that the main character is not likely to have gained a love interest by simply saying Hmm, I like her. And chances are that they argued about something at some point. It's the meat of character and setting that gets taken from your life experiances and your understanding of your world, layed down on the framework of the skeleton of the sequence of events that outline your story which is used to highlight a moment in the story that is meant to resonate in the reader.

That's just one example, I have several stories that don't use this system at all. Some start with a simple what if idea. and some are reactions to how absolutly bad some current works out there are and how they should have been done in my opinion (then you go back and hide the links to it origin, so the two could seem completely differant works, It's like writing a fan fiction, that fixes something that was badly handled in the story, then look at the setting and characters and see how differant you can make them and still keep the new idea valid, then go back and maybe alter the new idea to the point where you can readjust the setting again. Soon the work is not related to the original and yet it's complete and interesting).