Astronomer

Step 1: Obtain a Bachelors degree in science subject:
This is the first step required to get in to the field of astronomy. After higher secondary, candidate should obtain a Bachelors degree in science subjects such as physics / chemistry/ mathematics. Apart from these, some universities offer under graduation course in astronomy.
Step 2: Obtain a post graduate degree:
Those who have completed their graduation in science subjects such as astronomy or physics or chemistry or mathematics can look for master level courses like M.Sc astronomy, M.Sc astronomy and space physics, etc.
Step 3: Search for a career in astronomy:
After completing educational programs related to astronomy, candidate can search for a lucrative career in the field. At entry level one can get in to the role of junior research fellow, research trainee, etc. Job positions exists in firms like NASA, Association of Bangalore Amateur Astronomers (ABAA), Bhabha Atomic Research Centre (BARC), and Indian Space Research Organization (ISRO). Department of Science and Technology, Government of India also offer enough career openings. Inter-University Centre for Astronomy and Astrophysics (IUCAA), Technology Information, Forecasting and Assessment Council (TIFAC), etc. are some other firms offering rewarding jobs in this field.

The Indian Institute of Astrophysics is a premier institute devoted to research in astronomy, astrophysics and related physics. This is a full-time research program where in the students' work towards their PhD degree under the supervision of an IIA faculty. Students may join the program in either the first semester beginning in August or the second semester beginning in January.
Entrance examination is held in December followed by interview in January. Students passing the JEST exam are interviewed in May / June. The eligibility criteria for PhD at IIA is M.Sc. in mathematics / applied physics / applied mathematics / optics and photonics / instrumentation / electronics, etc. All around excellent academic performance from 12th to PG will help you fulfill your dream.
You are advised to opt for PCM at 10+2 stage. You are advised to do B.Sc. Physics or mathematics. You may then opt for M.Sc. in mathematics / applied physics.

The standard route to this is not as such reading any specific books at this stage (I'm not discouraging you from reading popular books on cosmology, which you should whenever you can). What you need is a strong background in Physics which translates to a strong undergraduate and graduate (Ph.D) training in Physics.
You can start specialising to Cosmology during 3rd or 4th year of undergraduate by taking courses on General Relativity, Astrophysics and possibly even Cosmology if the course is offered. There's also a question about experimental or theoretical Cosmology (which is not clear from your question) and as such the approaches very different. I'm not familiar with the courses focused on experimental aspects. So, I'll leave it at that.

Hi,
Following degrees from renowned institutes like IISC or IIT in Ph.D (Astrophysics), Ph.D (Geophysics), Ph.D (Metaphysics). After graduation, the candidates can appear for the entrance exam, which is held by the NASA for the recruitment of scientists, astronauts, etc.
Candidates can also find employment in ISRO. There are many openings in ISRO, which is conducted for the recruitment of scientists and engineers. In order to join the ISRO, the candidates need to clear the joint entrance exam set by the IITs.
Eligibility:
1. Citizenship: candidates who are joining the ISRO need to be Indian citizens.
2. Age limit: the candidate should be at least 21 years at the time of joining. The age limit is relaxable for candidates belonging to the SC/ST category.
3. Qualification: candidates need to be graduates from a recognized board or university.
How to prepare for exam and interview:
Candidates need to pass the screening test first. They should submit the application form online. Next they need to undergo tests in professional and psychological aptitude assessment, which includes behavioral and logical skills. After that they will go through a medical evaluation. The final stage is an interview where the candidate will be judged before he/she is selected. The candidates should remember that only 2 or 3 people out of scores of candidates will be chosen at the end. So, they need to be prepared for the toughest competition.
I hope this helps.