If you're going to do present tense do it for a good reason and mitigate the downsides.
Present tense lends a sense of immediacy to the work and also may make it feel like you are reading a screenplay or drama as opposed to a typical past tense novel. That's the good part. If you want urgency and a sense of being close to the action, present tense can help. Present tense is naturally suspenseful because it gives readers a sense that nobody, not even the narrator, knows what is coming.
Unfortunately the present tense comes with lots of downsides. It is not typical in English language novels. Charles Dicken's Bleak House in the mid-19th century written half in present tense is probably the first example of the present-tense in novels, which have a history going back to the 17th century. Your readers will notice your use of present tense, and that may make it difficult for them to read your book unless it's done quite well. Any time you step out of fiction norms it's best to do it artfully because readers will notice.
When something is happening in the present tense readers aren't going to expect a lot of narration. If your character is monologuing in the present tense while going through a car chase readers aren't going to believe it. Who has time to monologue while they are driving the wrong way down a one way at 30 miles per hour over the speed limit? On the other hand readers can believe a bit of a monologue if they know the narrator is not currently driving in the car chase, but rather remembering it.
Present tense flattens the story as well. Your present tense narrator is very close emotionally to the characters, especially if the narrator is present tense and first person singular. The first person singular, present tense narrator is mostly focusing on what is happening to him or her, and not the other characters. Your readers will have tunnel vision on your single main character. Even a present tense third person limited or omniscient narrator won't be believable opining on and on about how characters are feeling or even dwelling too long on actions that show how your characters are feeling. Present tense also keeps the story firmly rooted in the present, minimizing your ability to freely use the past and future. After all, how do you convey past information without changing tenses in this case? Future? How does time move? Do you use awkward phrasing like "later she does..?" This can be mitigated by having another narrator interwoven in your story using past tense, of course.
Do note that present tense is, if last year's controversy over Pulitzer Prize candidates using too much present tense is any example, becoming more popular and may therefore be becoming more acceptable to average readers.
I'd suggest reading some well-known present tense works before deciding to use the present tense. For example:
- Bleak House by Charles Dickens
- Rabbit, Run by John Updike
- The Time Traveller's Wife by Audrey Niffenegger
- Fight Club by Chuck Palahniuk
- The Siege by Helen Dunmore
- Wolf Hall by Hilary Mantel
- Bright Lights, Big City by Jay McInerney