Can Buddhism be called as Atheist, Agnostic or Theistic? I am reading this book currently called Buddhism without beliefs. In this book the author claims that Buddhism is Agnostic. Now Agnosticism is a claim that you are ignorant, or not sure whether God is there or not. I am sure that Buddhist suttas mention several gods, like Brahma etc. Also most modern scholars promote Buddhism as Atheistic, as there is no central creator. What's your take on this?
Yes, it can be called any of these three things; and it is called different things by different people, for the reasons you described.

Three further comments:


The terms (like "atheist") were originally invented and used by other cultures for other religions; for example, Socrates was (legally) accused of atheism and condemned (to death) for it -- so the distinction (between "atheism" and "non-atheism") mattered. I'm not sure how or why the distinction matters in Buddhism, unless it affects practice etc.
Buddhism as I understand it doesn't deny there are Gods (it doesn't say "there are no Gods") so it isn't atheist. But it also doesn't say "God can save you" in the way that Christianity does, or that "The purpose of life is to obey God" etc. The importance of Gods is de-emphasised, people are responsible for their own karma and their own salvation, so it isn't exactly like a Theistic religion either. The story of Siddhartha's going forth and so on is told (at least n the West) as a more-or-less human story.

Bhikkhu Bodhi's book In the Buddha's Words has chapter titles, "The Human Condition", "The Bringer of Light", "Approaching the Dhamma", "The Happiness Visible in This Present Life", which are this-worldly and human rather than other-worldly and Theistic.
Calling Agnosticism "ignorance" is a bit confusing when it's applied to Buddhism. "Agnosticism" means (etymologically) "without gnosis" or without knowledge (of God).

I might describe myself as "agnostic about God" if I have no personal knowledge, no personal experience, of God.

In the West people use "Agnostic" as a middle way between theist and atheist: "theist" means, "I believe in God"; "atheist" means, "I believe there is no God"; and "agnostic", "I neither believe nor disbelieve, I have no personal knowledge of it." (I probably wouldn't say that I'm "agnostic about Antarctica" -- I believe it exists although I haven't experienced it personally).

"Ignorance" is a term which features in Buddhism too: Avidyā (Pali: avijjā). Avijjā too means "without knowledge".

In Buddhism, though, it isn't used to mean "ignorance about whether God exists" (because, IMO, whether God exists isn't the important question). Instead it's used to refer to ignorance of dhamma, ignorance of right view, ignorance about topics like anatta (i.e. whether the self exists), anicca, and dukkha, and so on.