If you have settled the question of the existence of God once and for all, I suggest not reading further, as it will only aggravate you. For everyone else, full steam ahead!
Over world history, few people have been atheists. Presently, many are. In this country, most are. The assertion that one is an atheist typically draws neither ridicule, nor incredulity, nor censure. I certainly do not advocate the reintroduction of these responses. I do advocate an examination of the assumptions that underlie much atheist thought.
There are atheists who have received considerable and robust religious training and who, nonetheless, have concluded that there is no God. With those, I have the most sympathy. Most people, at least in this country and these days, have not received such training. There might have been some perfunctory and patchy exposure to religious questions, but there has rarely been any real engagement, and the instruction tends to have been by broadcast rather than dialogue.
The assertion I am an atheist, in this context, is apparently a reasonable starting point.
I would like to offer an alternative approach, namely that we start elsewhere, then see whether that is a reasonable ending point.
The theist and atheist positions both (largely) posit the existence and reality (in some form) of the material world. There they agree. Where they disagree is whether there is a second world, a spiritual world. The theist would hold that this spiritual world exists and, secondarily, is presided over by one or more gods. There will be those who hold, with the theist, that there is a spiritual world but have differing views as to the existence or position of a god or gods within that. For the sake of simplicity, let us reduce our camps to the two: those who hold there are one world, and those who hold there are two. The question of the existence of God is therefore subsidiary to the question of whether or not there is a spiritual world, since the God under discussion is held to be one of spirit not matter.
When an individual is presented with the proposition that there is a spiritual world, an unseen world, which is presided over by God, the question must, I believe, be taken seriously. In contrast to the assertions that we are controlled by lizard people, that the world is flat, or that ... (I should stop before I offend someone), the assertion that there is a spiritual world had been held by too many intelligent, well-educated, rational, sensible, and thoughtful people over history to be laughed out of court; indeed, physicists, computer scientists, and contemporary philosophers are not necessarily atheist: quite the reverse. They've read far more than you or I, for instance, about the nature of existence and consciousness for the theists among them to be considered hoodwinked dunces. The crackpot and charlatan are persistent but mercifully occasional phenomena. When views about the spiritual world have persisted in all ages, in all cultures, and even in a world where all of the arguments of the atheist are well rehearsed and well understood, the question is not resolved but it is firmly on the table. It is no good simply 'deciding for oneself' without some real examination (and by examination I do not mean casual considerations whilst staring out of the window of a moving carriage on the way to work). The reverse argument holds equally well: the theist should take note of the number of equally well-educated, intelligent, sensible, thoughtful, and rational atheists who have sincerely pleaded their cause, to their own detriment, to boot.
So far so good. The question is thus on the table, for both sides.
One could examine a dozen arguments, and I certainly do not propose to argue for the existence of God in any thorough way, but I do propose examining the question with sufficient open-minded to allow a real and indifferent (in the sense of unbiased) investigation. To do this, I will examine one argument.
The most common argument, and perhaps the most credible, is the assertion that there is no evidence for the existence of God. This essentially is a cipher for the assertion that there is no test that can be carried out under laboratory conditions that furnishes physical proof of the existence of the world of the spirit. The 'laws of nature' are often cited in support of this, and the matter is then deemed settled. Except it is not.
Whether or not there are two universes existing in parallel dimensions, or even many universes existing in parallel dimensions, is not something one would necessarily expect to prove by experiment. It is only if one universe had effects within the second universe that one might expect to be able to observe and correctly attribute those effects. Now, there are several premises even behind this expectation. If any of the premises fail, then the absence of attributable evidence does not prove the absence of said second universe. If the two operated independently, there would be no evidence; if the second affected the first in ways that are not observable (e.g. if the second universe actually caused the first to come into existence), there might be no evidence, or at least no retrievable evidence; and if there were no method for attributing to a second universe the ways in which it affected the first (e.g. if the second universe created what we think of as random events at quantum level), there would be no evidence. The same principles apply with the world of the spirit. The presumption must be that any second world would not necessarily be measurable using the devices of the first. The devices for measuring the optical effects of a sunset cannot measure a person's appreciation of it. These reside in different dimensions.
With regard to the laws of science: laws of science predict how things will operate, given baseline conditions, and provided there are no interferences. Train timetables do not predict late trains; predictions of the movement of billiard balls fail if someone takes a cue and strikes one; laws against theft do not predict whether your handbag will be stolen. Thus, such laws have more limited scope than is supposed. They tell us what event will occur if we mix two chemicals. They cannot predict if we will mix those chemicals or why those chemicals exist, why the person doing the mixing exists, or what the individual's purpose is. Interference by another realm in this realm need not cause a suspension of the laws of nature. It could quite clearly trigger events that then proceed in accordance therewith. The point is that the presumption that interference by one world in another would necessarily produce a disruption of the operation of the laws of nature that can be measured scientifically is a flawed one.
Similar arguments could be presented for all sorts of other textbook objections.
The point, of course, is not to prove that God exists but to question the presumptions sitting beneath the standard and apparently watertight objections held even by intelligent, thoughtful people. This is not to denigrate those people, for I have been one of them for much of my life. This is only to plead for wider reading, more considered thought, and an attitude of inquiry rather than begging the question one is seeking to resolve.